Strange bug, I was able to reproduce it with this setup in the attached image.
That is the standard unity 'Wide' setup with only playmaker 1.1 added.
Four things I noticed.
1. Once you get into this state, you can't get out without changing the layout.
2. The 'Actions' tab needs to be it's own window. If you make it a sub-tab like how the main 'PlayMaker' one is in that screenshot, the errors will not appear.
3. It needs to be below the 'Projects' tab for the problem to happen. I put it beside the projects tab by itself, but it didn't cause the errors (this one is strange).
4. If you open the 'Actions' window but don't dock it anywhere (leave it floating), it disappears. Perhaps this is normal, but seemed suspicious.