I never had reports of this issue after updating BIOS, try flashing to a lower version
I remind you that this motherboard is no longer supported by Intel technical assistance
I'm having the same issue with a DG31PR. After a Bios Update the KB and Mouse in PS2 sometimes are not recognized after restart and sometimes are. I'm thinking to downgrade the bios too, because I tried a lot of options at bios, but it isn't fixing...