Comment 51 for bug 727143

Possible temporary workaround:

I've had this problem quite a lot since upgrading while running matlab as others have commented. Once the error message pops up, answering yes/no/cancel all results in losing all window decorations.

However, if instead of answering the error message, if you merely minimize the error dialog, the window decorations continue functioning apparently indefinitely. I only have an N of one here, so YMMV, but until the patches come, it appears to work for me.