Tested on OSX 10.9.4, b6 64bit:
Install any ilok plugin without ilok software, so nag screen will appear. It usually hides here behind the renoise window. that window you can can move away, but if u even rescanned from prefs window, the prefs window won’t be movable, so only a force quit will help.
I have seen this also with some popup requester on synthmaster2 and old gear like pro53? with a bunch of plugins.