I just ran into a weird problem.
If I select all in a layer, copy and paste, nothing happens. If I try to rotate something in any layer it doesn't work. I can see the actual tool rotating, but whatever's been selected doesn't move.
If I copy and paste into a new file, I just get a white rectangle instead of whatever was copied. However, all this works fine if I open some other file. I've never seen it do that before.