Vista - Large file transfers fail (hang) on Vista 32bit

I've been having some increasingly problemactic issues with my Vista system.

Issue:
Large files (anything from 700MB up) tend to completely stall if transferred
from either my main drive to an external USB drive or network system.
Windows Explorer process cannot be closed. The system needs to be restarted
(it does log off but doesn't fully restart on its own) in order to clear the
transfer window. The file transfer window will get stuck at a certain point
with the timer not going anywhere (even if left for hours).


I initially suspected a bad network card driver (I'm using a D-link DGE560-T
card, Yukon based) but noticed that it happens while copying to other media
like my external 500GB USB drive.

The system is running on an older Nvidia nforce4 AMD platform (XP 4400+)
with 2GB of ram, RAID 0 C drive (2x250GB). The nvidia drivers have been
updated to the latest but no changes.

I don't even know where to look... my main Media Center Vista system seems
to be able to copy files from my Vista laptops just fine so I'm quite baffled!

Any ideas?

No solution but I have the same problem:
I cannot send emails with largish attachments (currenlty 3Mb stuck in my outbox) through my wireless connection to a Netgear DG634G;
I have purchased a Canon printer that is connected to the router by Ethernet and cannot print more than a few lines of a page before it aborts.
If I connect the laptop to the router by Ethernet cable then all is OK.
Computer is a Dell Vostro 1500. The wireless card is Intel Prowireless 3945ABG. Logging
I have another laptop running XP and there is no problem with emails or printing. The guilty party must be Vista 32.
Using Vista Anti-lag doesn't seem to work.
Any ideas out there?

I've resolved this issue... My AV software, SAV Enterprise 11 was blocking
file transfer. Disabling the product would allow consistent transfer w/o any
hang...
Slowly losing faith in Symantec, especially with the many issue I've had
with their virus detection (doesn't pick half of the threats that I deal with
at work). Moved on to AVG, works wonders and it's free.