Not sure, what I did, and I haven't managed to reproduce that bug yet, but I opened the tips and tricks tutorial, went back to my document and was not able to select a tool anymore. I could select all the toolbuttons and have them all pressed at once, but there was no way to change the tool from caligraphic pen to anything else. also the dialogs would be behind my window. When I closed the tutorial, everything worked fine, but reopening it messed up things again. Restarting inkscape turned out to be a way to get rid of that problem. But as I said, I have not managed to reproduce it yet.

David