The BSOD and freezing might be the same thing, manifesting itself in different ways pre/post flash. Reflashing to an old BIOS is something that can cause issues on some boards/equipment, depending on what the manufacturer designed for. Rolling back a firmware flash generally falls well within the 'unsupported' parameters though.
You really should seriously be looking at a motherboard replacement, either RMA or purchase. There's a few things you can test with the RAM which have already been mentioned but it's highly likely that this is an issue with the mobo.
The only other thing you could potentially try is getting an OC tool (CPU OC) and pull down the voltage by a smidge, like 0.05-0.1v or whatever. You might have gotten a slightly underperforming/unstable at stock CPU.
Once I have narrowed down this issue more I will probably rma the board first but I'm not just going to do it to do it, it's too much hastle, and then what if it isn't the motherboard and it was something else all along. I'd like to narrow this issue down more if possible.
