I have one of these PCIe-x1 Firewire cards that I've had for a few years, working fine under XP. Newegg link.
While installing Windows 7 RC this afternoon (and stripping out every component, then adding them one-by-one), when I added this Firewire card, the system would hang at the Windows 7 login screen, after two or three characters.
Any suggestions on things to try? Taking out the card again everything boots normally. I have a Dell E510, 2GB RAM, which unfortunately doesn't have built-in Firewire.