I've not seen the big black bars at top and bottom for a few days now, but As an extra treat here's a new one I just bumped into.
After using a few VMs on this macbook pro today I now had one freeBSD, one Windows XP (x32), one Windows 7 (x64) and a Windows Vista (x32) running. After suspending and closing the Vista one, there was no windows VM in the windows list anymore, only the freeBSD one.
But sure enough the XP/Win7 was all still running when swiping on the track pad. I double clicked on the library window and now I've got myself 2x Windows 7 running (it's the exact same copy, just as if there are two monitors attached who clone each other)
See screen shot 
and check top right and bottom left.
Oh and for the record I edited out 1 VMs name.
edit: Remind me to not mention that I've not seen the black bars at top and bottom for a few days as then they'll come more often.