There are allot of failure points with an external drive. Any of the following could be the problem:
- eSata port on your TiVo
- eSata Cable
- eSate Port on external hard drive
- varous other parts of the enclosure like the power supply etc.
- The actual hard drive in the enclosure
I have used 2 enclosures both had problems with the cables. I would unplug everything (power to TiVo, power to the enclosure, & both ends of the eSata cable) then plug back in the eSata cables, then the power to the enclosure, then the power to your TiVo.