Windows 7 can't upload file larger than 300kb

Hello everybody, I'm looking for solutions for my problem.

My scenario:
My workplace upgraded our OS from Windows XP x32 to Windows 7 Enterprise x64. Since then whenever I want to upload a file that is larger than 300kb to our EDMS server (web based), I always got timeout.

I installed windows virtual pc with windows 7 x32 (I didn't installed any software on it except firefox 4) and tried to upload the same file, I still got time out. I was using Internet explorer 8, firefox 3.1, and firefox 4. They all gave me the same result.

More information:
Server:
Windows 2003
IIS - Apache/Tomcat

EDMS Software:
Java
No more support for the software since it is an old software

Desktop PC:
It's already been customized by our computer tech support and I don't have admin right to the desktop computer

I've already tried in my virtual pc:
a. disable IPv6
b. disable autotuning

Anybody knows the solution for my problem? If I do need some tweaking, please tell me with detail how to tweak it. Thank you for your time and help.

Regards,

Andy

Ping statistics:
Packets: Sent = 9, Received = 9, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 1ms, Average = 0ms

Thanks for the fast reply.
My desktop is using Symantec Endpoint Protection. My workplace has been using it since windows XP. I don't think the software is the problem, because I tested with my virtual PC with no antivirus installed and I got the same result.