TGP-5 surround modes vanished

My TGP 5 has developed an odd problem. It does not toggle through all the surround modes it's supposed to have!
Using the left direction button, remote or chassis mounted, it only toggles back and forth between 'Stereo' and 'PLIIX Movie', and using the right button it adds 'Party' into the mix, switching through the three modes in turn, although it often jumps back to 'PLIIX' Movie' by itself.
All the other modes just don't exist anymore. Jazz Club, Neo6, Matrix, all gone.
Does anyone in the know think this might be a software corruption issue or would it be a hardware issue?

Have you checked the "Troubleshooting" section of your manual? I'm not familiar with the TGP-5 as it changed dramatically from the TG-IV

Well I went through the 'restore factory defaults' procedure last night and it fixed the issue. Hold the power and tone down buttons until it reads 'restore...' and then powers itself off.
Of course then I had to restore all the custom settings, but it works!

Congrats!! Some of the TGP-5s out there are still under factory warranty, 5 years from date of manufacture. I believe there is downloadable firmware updates that should be installed if they haven't been already.

http://www.sunfire.com/downloads_archive.asp

Congrats on the fix.