Would you happen to be using the DisableLoadingMip0="1" fix (GamerProfile.xml) for stuttering? I never experienced any quick blackouts in the game, but soon after I used this 'fix' I saw it happen for a moment after playing with the terrain detail settings. This was at the end of the gaming session I just played and I've yet to test more to see if it happens again. I just thought I'd post to say I've at least seen what appears to be the same thing. If it happens again next time I play I'll try to remember to come back and post more details.