Sounds like the hard drive may be failing. If it continues, you should look at weaknees.com for replacment drive options. Their upgrade kits are pretty easy to use. If you're a bit more comfortable, you can get your hands dirty with a bare drive and InstantCake from dvrupgrade.com. dvrupgrade.com also sells kits.
Since you only have a 40GB drive, you might want to use TivoToGo to save any programs you'd like to keep on a PC. Just remember that if you start with a new drive, season passes, settings, and your saved shows are lost because they're stored on your old drive. When you install the upgrade kit, you will also need to re-run your guided setup as if the Tivo was new. Both sites do an excellent job of explaining the details.
Since you only have a 40GB drive, you might want to use TivoToGo to save any programs you'd like to keep on a PC. Just remember that if you start with a new drive, season passes, settings, and your saved shows are lost because they're stored on your old drive. When you install the upgrade kit, you will also need to re-run your guided setup as if the Tivo was new. Both sites do an excellent job of explaining the details.