If you are having this problem repeatedly, you may need an RMA (and, trust me, I'm not one to recommend RMA's lightly!). I have seen this issue before, and the only possible explanation is a bad bit in the E²ROM that holds the working copy of the BIOS. This diagnosis has been reinforced by the fact that, in a couple of cases, the problem could be cured by loading a different BIOS, where my assumption is that the bad bit which is 'stuck' at, say, 1, is actually
set to 1 in an alternate BIOS copy. The symptom here is that you get a BIOS checksum error, the board recovers, you reload the copy of the particular BIOS that you've been using, and you have the problem again. In some cases, the problem occurs without you loading a BIOS, and my assumption there is that the 'as shipped' BIOS which restores itself has a 'conflicting bit', so when it autoloads, it triggers the whole cycle again...
The things to try:
Make sure your BIOS copy is good - try D/Ling it again, from a different source. It is possible to have a corrupt BIOS pass checksum - don't ask me how, but I've had it happen!
If you are willing, and the older BIOS 'cooperates' with your hardware (especially verify that your RAM works), you might try loading a different BIOS revision - possible to 'get lucky' and have the bad bit 'match'...
Other than that, it's time to
contact GB regarding an RMA...