Can't pause/resume sync

I'm using LR CC 3.3 on a Mac with current OS.

If I push "pause" synch, it doesn't pause.  Instead I get the spinning wheel in the center of the screen, which goes on indefinitely.  Ultimately I have to quit/restart LR, which I can do only from the Force Quit menu since the entire program is hung.

This started only after the "upgrade" last week which has been nothing but buggy.  Is there a way to roll back to the last stable version?