Unable to drag line breaks

I have been using Musescore for quite some time and seem to have put the system into a mode where I cannot drag line breaks (or anything else) from the palette. I upgraded to 2.0 (long overdue), but that didn't fix the problem. I can't drag from the new location on the left, either. Any idea what switch I flipped. The problem is pervasive - it won't work on new scores or old ones that I previously had breaks on.