I think windows can't resolve the dialog box command - and just gets caught in some loop.   I've noticed some times, I can click "ok" wait a minute, click it again, and then it goes away - but acts up from there on out.   Other times I click "ok" and that's it, it's going to just sit there, even if I wait and click again, I then get the "do you want to wait or quit" question.

When it's working correctly, I just click "ok" and instantly it goes away.

Maybe a memory leak?

I came, I rendered, I'm still broke.