If either drive on a TiVo with an external drive goes bad, you will have problems. Unlike a PC, a TiVo spreads its recordings and other storage across both drives. You may have to "divorce" or remove the external drive and see if the behavior still exists. Doing this will remove recordings, so be forewarned.
S1 (Recycle heaven)
Series 2 (PLS)
TiVo HD 1Tb (OTA, PLS)
Do the 3 R's to be GREEN, Reuse/Recycle/Recharge and RECHARGE the earth!!
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!