Strangest BIOS problem

Abit NF7 motherboard. Recently a problem developed...
Bios doesn't display correctly. System Posts fine, will boot and is stable (ubuntu). Press 'del' to go into bios and all I see is black screen and flashing cursor (can't input). I have the latest (22/10/2004) bios and have tried reflashing, refrash was succesfull but didn't fix. Also have removed PCI cards but get same problem.
any ideas?

to add.. its a home machine and I've not done any fancy overclocking tricks this time.

Problem solved.
Turned out to be caused by one of the fans - I unplug a case fan and it worked. I assume electical noise or something.
New one on me, but glad its fixed :)