I'm running Linux Mint 12 and Cinnamon 1.4 in Virtualbox 4.1.14 under Windows 7, 64bit. The display adapter is NVIDIA GeForce 405. For Virtualbox, I have video memory set to 128 MB and 3D acceleration turned on. Cinnamon works great for about 2 days in this configuration, but then it will start to flash to a black screen when switching windows or, for example, when chaning browser pages. The screen goes momentarily black and then comes back. The only fix I have found is to shut down Mint and restart. This is a real pain because I often have tasks that need to keep running. This does not happen if I use Gnome as my desktop, but I really prefer Cinnamon. Any clues about how to prevent this or how to recover when it occurs would be appreciated.