Crashes while copying larger files

Hello everyone,

I bought a new computer and installed Vista Home Premium x64 on it, and most of the time it works fine. However, when copying a somewhat larger file over the LAN or downloading a larger file, the computer crashes. I don't know what the maximum file size is exaclty but I think it's a few MB.
When I copy a file that is too large, the monitor turns black (although the standby light doesn't change, so the monitor itself stays active), the sound starts to loop or just stops and sometimes the rear fan starts spinning at top speed.
Small files can be copied through the LAN or internet without problems and copying large files from an external USB HDD works fine.

Does anyone know what the problem can be?

System specs:
Gigabyte EP35-DS3 motherboard
Dual core 3.0GHz processor
ATI Radeon 4850 graphics card
4GB RAM
320 GB HDD
550W power supply

Thanks in advance for anyone who can help me.

Verify first that your lan controller drivers are fully 64 bit compliant.

What cabling and NIC speed,duplex do you have? Is it on a switch or router? Do you have the proper drivers and security setup.

The computer is connected with a switch, through a UTP cable.

But I think the problem may be solved already. I checked the website of the motherboard for drivers, as I have an on board network adapter, but I already had the newest LAN driver there. Just to be sure, I also checked the website of the manufacturer of the network adapter and there was a newer version. After installing that one, I could watch a video that made the computer crash before installing the new driver.
I will try some other large files too, but the first result seems promising.

Thanks for the help.