Several times I have noticed that if I use Honeycomb's app switching to jump to another app like the web browser, then switch back to PS, PS restarts itself, which loses any unsaved work.
I tested switching to other open apps including my browser myself but as of yet have been unable to reproduce this. I'll keep testing, in the meantime I would suggest saving any projects as a workaround.
Yeah it didn't always happen, just a couple of times. Saving often is always a good plan with any software. That does bring up one other thing though, it would be nice if there was a way to save without having to jump back to that main screen every time.
That's a good suggestion Philnolan_3d. Here's the Idea section in the Photoshop Touch forum where you can post requests and ideas for Photoshop Touch. The product team will look at these regularly and your idea might influence future versions of Photoshop Touch.