This just happened to me to. Go to Preferences under either File or Edit (can't member which). Click it to "Launch to Factory State". You will have to close it and then open it again....so I suggest you save a *.pz3 of what you are working on first. Then just launch it again and open the *.pz3 and you should be back where you were. I hope what you described is what happened to me...sounds like it...but ya never know.