Seeing a bunch of requests that look like they were altered and not the original request from the client machine.
Here are some of the IP addresses that had this weird header issue recently:
11/23/2009 8:57:02 PM 76.104.180.131 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0)
11/22/2009 8:32:58 PM 71.234.217.226 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; FunWebProducts; Comcast Install 1.0; GTB6; .NET CLR 1.1.4322)
11/22/2009 7:39:31 AM 63.226.217.184 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; .NET CLR 2.0.50727; IEMB3;
11/22/2009 7:10:29 AM 173.66.61.177 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322; InfoPath.1)
11/21/2009 6:57:42 AM 67.40.212.30 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; .NET CLR 2.0.50727; IEMB3;
11/20/2009 5:11:09 PM 67.161.88.107 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Comcast Install 1.0; GTB6; .NET CLR 1.1.4322)
11/18/2009 4:54:27 PM 209.91.40.80 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.0 (KHTML, like Gecko) Chrome/3.0.195.33 Safari/532.0
11/17/2009 9:02:20 AM 216.254.19.10 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)
11/15/2009 6:11:47 PM 98.247.251.172 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; MathPlayer 2.10; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729;
11/15/2009 10:06:02 AM 76.22.123.218 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322)
11/14/2009 11:45:21 AM 98.174.211.179 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0)
11/14/2009 9:46:00 AM 174.113.26.207 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 GTB5 (.NET CLR 3.5.30729)
11/14/2009 4:06:48 AM 96.18.203.27 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; FunWebProducts; GTB6; .NET CLR 1.1.4322)
11/13/2009 9:16:07 PM 67.171.37.175 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.1) Gecko/2008070208 Firefox/3.0.1
11/13/2009 8:22:26 PM 24.113.197.5 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322)
11/11/2009 10:31:57 PM 96.26.232.125 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322)
11/11/2009 12:46:39 PM 98.237.128.105 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; Zune 3.0; .NET CLR 3.0.4506.2152; .NET CL
11/10/2009 8:52:51 AM 71.37.54.113 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 3.1)
11/8/2009 7:52:24 PM 75.111.19.240 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15
11/7/2009 10:50:38 PM 71.227.255.37 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
11/7/2009 10:50:12 PM 71.227.255.37 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)
11/7/2009 5:45:34 PM 24.17.66.221 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; Zango 10.3.85.0)
11/7/2009 4:03:05 PM 71.227.155.229 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 (.NET CLR 3.5.30729)
11/7/2009 1:00:12 PM 67.185.148.232 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; Zune 3.0; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
11/5/2009 10:59:14 PM 67.171.34.181 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0)
11/5/2009 6:30:41 PM 66.8.185.228 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
11/5/2009 4:42:05 PM 67.171.34.181 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0)
11/5/2009 4:09:26 PM 67.171.34.181 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5
11/5/2009 2:09:18 PM 67.171.34.181 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0)
11/5/2009 1:55:29 PM 71.194.250.75 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15
11/3/2009 5:49:21 PM 24.18.214.26 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.4) Gecko/20091016 Firefox/3.5.4 (.NET CLR 3.5.30729)
11/3/2009 9:24:01 AM 98.232.12.107 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)
11/3/2009 9:21:40 AM 96.26.255.77 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)
11/3/2009 9:05:57 AM 24.18.227.177 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322)
11/3/2009 7:07:03 AM 97.113.236.36 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322)
11/2/2009 5:29:23 PM 207.172.136.97 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322)
10/30/2009 11:44:14 PM 67.183.56.30 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6.3; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30
10/30/2009 11:44:13 PM 67.183.56.30 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; GTB6.3; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30
10/30/2009 11:44:27 AM 131.191.65.125 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322)
10/27/2009 6:28:27 PM 71.112.251.46 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.3072
10/27/2009 6:28:27 PM 71.112.251.46 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.3072
10/25/2009 8:25:20 PM 174.21.95.103 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)
10/24/2009 4:36:59 PM 75.92.212.208 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; Zune 4.0)
10/22/2009 3:25:26 AM 69.85.109.91 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727)
10/21/2009 12:55:41 PM 24.16.92.189 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
10/19/2009 5:03:33 PM 76.28.193.198 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 GTB5
10/17/2009 10:07:48 AM 24.18.214.26 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)
10/13/2009 12:39:53 PM 98.225.57.246 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322; WinTSI 10.10.2009)
10/11/2009 10:19:35 AM 209.143.5.210 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 2.0.50727)
10/10/2009 1:47:04 PM 64.136.26.227 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; InfoPath.2; .NET CLR 2.0.50727; .NE
10/6/2009 7:59:57 PM 63.226.219.30 Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; .NET CLR 2.0.50727; .
10/6/2009 1:52:07 PM 64.146.149.194 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322)
10/5/2009 5:20:18 PM 67.160.3.12 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 3.1; .NET CLR 2.0.50727; .
10/5/2009 4:57:52 PM 98.232.9.64 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.11) Gecko/2009060215 Firefox/3.0.14
10/4/2009 5:28:20 PM 75.92.211.243 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
10/3/2009 8:40:36 PM 98.117.109.217 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.14) Gecko/2009082707 Firefox/3.0.14 (.NET CLR 3.5.30729)
10/3/2009 4:45:31 PM 71.227.155.229 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.14) Gecko/2009082707 Firefox/3.0.14 (.NET CLR 3.5.30729)
10/2/2009 3:56:39 AM 161.53.179.226 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)
10/2/2009 3:55:57 AM 161.53.179.232 Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)
10/1/2009 8:36:55 PM 67.171.39.2 Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.14) Gecko/2009082707 Firefox/3.0.14
10/1/2009 4:49:42 PM 70.193.96.120 Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.2; MS-RTC LM 8)