I have had similar problems in the past.

Some things that can be done to help are:

1. Close searches before closing Xolox.

2. Wait 10 seconds each before closing the “popup error boxes”(1st two).

3. Ctrl+Alt+Delete+Enter (repeatedly) will eventually close that EVIL “error box”.

It never happen to me if there was no activity, (no downloading, uploading, or searching when I closed Xolox).