Apache upload failed when file size is over 100k

Below it is some开发者_Python百科 information about my problem.

1. Our Apache2.2 is on windows 2008 server.
2. Basically the problem is user fails to upload file which is bigger than 100k to our server.
3. The error in Apache log is: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. : Error reading request entity data, referer: ......
4. There were a few times (not always) I could upload larger files(100k-800k, failed for 20m) in Chrome. In FF4 it always fails for uploading file over 100k. In IE8 it is similar to FF4.
5. It seems that it fails to get request from client, then I reset TimeOut in Apache setting to default value(300) which did not help at all.

I do not have the RequestLimitBody option set up and I am not using PHP. Anyone saw the similar error before? Now I am not sure what I can try next. Any advise would be appreciated!

Edit: I just tried to use remote desk to upload files on the server and it worked fine. First thought was about the firewall which however is off all the time, Http Proxy is applied though.