Please try the following:
Download the latest driver
Extract the .zip or .exe to a floppy disk.
Remove the 2500 listed in Device Manager.
Run ATSetup.exe from the driver disk.
Shut Down and move the 2500 into a different PCI slot. Restart. Windows will re-detect the card.
You will have to re-set your network settings in Network Control after installing the new driver.
It sounds like a conflict problem with another hardware device such as a sound card, modem or video. Usually changing the card into a different PCI slot will change the IRQ and resolve the conflict.
To resolve a hardware issue you can also try to change the IRQ settings for those cards in Device Manger.