I have what appears to be the same issue with 4.1.2. Full Screen on dual monitors does work well for me with the exception of this resolution reset issue several times per day. This happens after unlocking my iMac, then unlocking my Windows 7 VM.
My 2nd monitor doesn't go black, but the resolution changes to something incredibly low (I'l check the resolution the next time this happens). I was Fusion 5 would fix this issue, but I now understand that this has been an issue since v3?