Try the three button reset. Hold down the Power Button and both volume buttons at the same time for 15 seconds and then wait 1 minute then hold the power button only until the red light flashes then release it and wait for the PB to reboot which will be about 4 minutes. This should get rid of all glitches in your PlayBook. Report back.
A big thank you for your online information. I had exactly this problem after wiping and resetting my PlayBook. I found your message after looking on a search engine; I followed your instructions to the letter and now all is back to normal. Thank you!