The TV Pack is very unstable and you might as well get used to things like this happening. I'd recomend going to 7, which is 5X more stable.
Anyways, what you need to do is resetup the TV data from scratch. To do this stop all the Media Center services and processes, then delete this directory.
%ProgramData%\Microsoft\eHome\mcepg*.db
Now reboot and the next time you launch MC it will prompt you to re-run the TV setup.
I probably had to do this once a month when I was running the TV Pack, which really sucked because it took me like an hour to add all my channel mappings and series recordings back in. One thing I did to prevent this was to make a full image backup at 4am, then on the days it did something like this I'd just restore. Still a big pain, but not as bad as setting it up from scratch.
Ben
How good can it be, if it isn't HD?
Engadget HD