Yes, I have the latest BIOS from April 2010. My previous BIOS was from 2009 or so, but both BIOS versions were newer than the 4890.
My mobo is an i7 1366 dx58so, so I doubt it's because the card is too good for the mobo.
My mobo manual doesn't mention what a long continuous series of beeps represent.
The beeps is what made me think of it, because thats what mine did. At the very least try that card in another computer and see if it works.