Upload Fails (Speed Tests)

My wife's Samsung laptop started exhibiting problems when she tried to upload attachments to web-based email. I eventually ran a speed test (on several different sites) and found that while the download portion of the test was great, the upload portion always failed. It actually seems to run but slows down and eventually times out. Several other devices using the same wireless router work fine. I've tried several things:
- Rebooted the router
- Taken down the firewall (Windows)
- Completely removed the virus software (AVG)
- Ran virus and malware checks
- Rebooted in safe mode with networking

All have no effect except rebooting in safe mode. Then, the upload works like a champ! So, it seems to me something is running that is blocking the upload. I've even went into MSCONFIG and systematically disabled services to see if any of them were the problem, again to no effect.

I'm pretty much out of ideas... Anyone help?

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: Intel(R) Core(TM) i3-2350M CPU @ 2.30GHz, Intel64 Family 6 Model 42 Stepping 7
Processor Count: 4
RAM: 6057 Mb
Graphics Card: Intel(R) HD Graphics Family, -1259 Mb
Hard Drives: C: Total - 432127 MB, Free - 298869 MB; D: Total - 24634 MB, Free - 24505 MB;
Motherboard: SAMSUNG ELECTRONICS CO., LTD., 300E4A/300E5A/300E7A/3430EA/3530EA
Antivirus: avast! Antivirus, Updated and Enabled

Thanks!

kep