Hi, I've had a problem for ages (many versions back). I usually use guest in full screen (Host-F). If I leave full screen and reenter again, the screen gets completely garbled (see attached photo). If I resize or move the window slightly before I enter full screen again, it works alright.
When the screen gets garbled I have no problem leaving full screen and go back to windowed mode again - but then, the window always gets resized to cover the whole desktop area. My solution for several years now have been to always do a slight window resize before entering full screen. Safe, but a bit annoying.
Same behavior in Windows 7 (64 bit) and Windows XP (32 bit). Still a problem in VirtualBox 4.1.2. Had it for several years.
Anyone else discovered this?