I suspect it is a software error that occurs only when certain circumstances happen. This can be hard to pinpoint the exact cause.

The Warranty is 12 Months, and if it is deemed faulty it should be swapped out if it is within this period.

That said a clear and delete everything does as the name says (including recordings), but in essence you start with an almost Virgin TiVo again. So you would likely get around the issue for a period of time and be no worse off than if you swapped units.

Peter.