Out of the blue, the current frame from the active timeline will suddenly go full-frame on my monitor, showing nothing on the desktop, and not want to leave. I have to resort to using Windows Task Manager to remove it. It usually occurs when I have left PPro to do something else, like look up something in help, find a file, etc. It will occasionally also run as a full clip as well, but this does not happen often. Usually, it will just be the static frame from the program window at the time. I have looked through the settings and have found nothing amiss that I would expect to cause this phenomenon. It does not seem to be related to the file or sequence type.
My software is up to date. I have a i7-970 hexacore machine running at 3.2GHz with 24GB ram and a Nvidia quadro 3800 card for GPU processing. I generally work in DVCPRO-HD, ALL-I.mov and AVCIntra-100 based files.
Any guesses? Never had this happen before, and I've been using PPro since 2003 in some form or another.