This has happened, allegedly, twice now, i've been working on photoshop under wine, and the unity 2D interface suddenly just dissappears, when i log out, everything closes, but it just stays on a screen with my wallpaper showing.

i had to force a shutdown both times, which i didn't like

it's only just started happening now i haven't changed anything Ubuntu wise. installed a few safe things here and there.

what's up with the interface, and how can I stop/prevent it from occuring?

Spec:
CPU: AMD phenom IIX2 55, 3.1Ghz
GPU: AMD Radeon HD 4550 512Mb
RAM:3GB
HDD: 160GB Hitachi