In RHEL and Fedora, you can change the IRQ of a network device in their setup dialogs. Run system-network-config from the command line, and look in the tabs. Hope this helps, although a google search revealed many other ppl with the same issue. One thread suggested to boot windows, activate the card then boot Linux, another reminded to turn on the network card with a keystroke combination.
But I assume you already did both of these?