iTunes fails to quit

Hello all.

Since the latest update my iTunes fails to quit consistently.

The app continues to work without problem, seemingly IGNORING any attempt to quit it in any way.

No quit through menu, Command+Q, Dock icon quit or machine shutdown (fails stating that iTunes prevented it…).

Everything keeps running and all I can do is to resort to a "force quit"...

Another strange behaviour is that now iTunes fails to connect to iDevices set to wifi-sync with it.

I had reliability problems with wifi sync before, but now nothing works anymore.

iTunes fails to connect to devices even when connected through USB sometimes!

I've repaired permissions multiple times, reset PRAM and whatnot… nothing seems to solve this problem.

I've reinstalled 12.1 with the downloaded version as well, to no avail.

Is there any preference or else I can erase to make it rebuild the files again?

I'm out of options… please help!

Next step would be to erase and reinstall all the OS… but I wouldn't want to...