Cannot download file from email and/or windows update

Archived from groups: microsoft.public.windowsxp.hardware (More info?)

Hi all,

I have 2 home PC run both running XP Pro with SP1 and have updated all the critical patches.
Both PCs can go on-line via router without any problem.
Yesterday, one of my PC took hours but couldn't download files from my email attachment (a very small file of 4K).
Usually I could download a 20Mb file with just 15 seconds.
I have tried to download files from other email services with the same result.
The download file window opened but it never start to download and the estimated download time didn't show any time at all.

The only change to the system was that I bought a new printer Epson R310 last week and I have added a NEC PCI USB 2.0 card for the printer as it use USB 2.0

I have checked device manager/hardwares and windows showed all devices are working properly and without conflicts.
I ran norton system works & Ad-aware 6.0 (latest virus definitions & reference files) and Spybot S &D, there are no virus or spywares found.

I have removed Zone Alarm version 4.5 with the same result.

I have tried every possible means that I known to fix the problem without success:
1. Clear internet cache, cookies and history
2. Reset internet security to medium (default)
3. Change the Lan settings by uncheck the Boxes "Auto detect setting" & "Use auto config script"
4. Check the services to ensure all necessary services are started/restarted
5. Re-installed IE. After re-installed IE, I went to windows update site to download the patches. There are 4 critical updates and the download file window opened but it never start downloading. I have changed the catroot2 file to catroot2 old but it still couldn't download. I have also restarted the cryptographic services.
6. I have changed the RJ45 cable (cat 5E).
7. I have tried to direct connect to my ADSL modem
8. Finally, I have clean installed XP Pro but the problem still exists

PC configuration:
Mobo - Asus P3V4X, BIOS version 1005
CPU - PIII 500MHz Copper Mine overclocked to 667 MHz
Ram - 256Mb PC133 SDram
Lan Card - Buffalo LGY-PCI-TXL with driver auto-loaded from XP
Sound card - Creative Sound Blaster Live with latest XP compatible drivers
Vedio Card - Creative GeForce Pro with latest nvidia WHQL drivers
NEC USB 2.0 PCI card
Epson R310 printer with XP compatible drivers


Can any expert help me to solve this problem ?

TIA



--
Peter