Sounds like its either a bad video card, bad bus slot or other, look here.
http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4ADFA_enUS347US347&q=pci+parity+error
you probably just needed to reseat it. a bad connection can do that.
Also, some boards that use PCI-E 1.1 and sometimes that can have issues with PCI-E 2.0 ans 2.1 cards. example, someone said that a 4850 doesn't work in a P5N-E Sli because of that. well my 4850 worked perfectly, but the card was faulty. my 5770 doesn't have issues.
I think a BIOS update would have solved that anyway.
lol, i didn't say go and update the BIOSyou sure you got the latest one?