I dont think it as anything to do with the formatting of the disc. I also have two panasonic dvd recorders and this crops up from time to time, sometimes when i have set to record. The fault isn't listed in the panasonic manual, but i find that switching the power of for a couple of minutes usually does the job. If it is a new machine contact your seller for advice.
yeah ive had the thing for few years now and it only does it now and again, just seemed lately to be doing it alot. i just switch it off for few min its just very annoying!!