It's most likely an IRQ conflict between something and the network card. Look at /proc/interrupts. Have a look at the output of dmesg if the kernel has found your card.
Chances are, if you run: cat /proc/pci you will prolly find that the card is not assigned an IRQ.
If it is a PCI card it might be possible that the BIOS is set wrong. Some motherboards will let you assign particular IRQ's to certain PCI slots. Disabling "plug and play operating system" might solve your problem as well (doing that will tell the motherboard that it has to assign IRQ's to all devices rather than leaving it to the OS to assign them).