Before imaging from scratch...

Have you tried a "Clear & Delete All" (NOTE: will delete all programs on the TiVo HD, as well as all settings, season passes, etc - i.e. it really means ALL). A month ago, I helped my bro change from port 80 -> 8000 and after digging/asking around quite a bit, found out that this was the only way to fix it (for non gurus).

We did manage to drag off the shows first (and the reloaded the good ones after) - but that's another story...