It seems like some 770s produced in 2006 had the WSOD problem. The early ones from 2005 and those from late 2006 work fine. I bought my 770 in Oct 2005 and didn't experience such a problem, although I flashed and rebootet it a lot.

On defective units, the WSOD can happen when rebooting due to (if I understood correctly) some race condition in powering the components.