I just set up everything and it came out ok. Is it possible you just added the overlay twice? It would be odd that the second overlay would be cut off at the board edge, but try starting again completely fresh.
edit: since you say you "keep" getting the error, I am guessing you have tried started over. What versions of everything are you running, and do you have the latest maps?
It sounds like your java process got corrupted. You don't have to restart your computer if you can figure out how to shut down the java process, but restarting the computer will do it if you don't know how to shut down the java process.