一段时间没有用这个apache，突然之间发现apache不返回东西了，抓包发现不管发什么请求，这个apache总是返回：
Request header field is missing ':' separator
重启apache，关掉重开，卸掉重装，折腾半天后还是选择google了，原来早有人郁闷过这个问题：
http://www.apachelounge.com/forum/viewtopic.php?t=602
Just spent half of night googling.
The main reason that I switched to 2.2.x branch is mod_proxy errors like
"Request header field is missing ':' separator." when accessing sites localhost sites.
Somewhere I read that it might be fixed in 2.2, so that's why I'm here.
After 3 weeks building all neccessary modules putting and tuning all together I see the same error =/
Problem was in Nod32's IMON module. It for some reason duplicates request. I disabled it and all works fine again.
http://issues.apache.org/bugzilla/show_bug.cgi?id=34716
Posting it here to help other with issues like this.
一模一样的现象，一模一样的原因。把nod32的imon（也就是网络监控）禁用了就好了。