Update: emailed Tivo with the issue and they asked for some numbers from the diagnostics. The signal strength was good on both tuners, but there is a 'RS Corrected' and 'RS Uncorrected' set of numbers on each tuner that indicates how clean or unclean the signal is. Tivo indicated that those numbers were really high, and they said in those circumstances, the tivo can see performance issues trying to deal with all the corrections, which can cause the freezing. They said to call the cable company. So there is a guy here literally as I type this. He already replaced a frayed cable end, but that hasn't corrected the issue. I just heard him call for backup so something weird must be up.
*crosses fingers that it's not a bad HD!*