I just found this thread and I am in exactly the same boat as the original poster. Same errors, same output ... no Mythfrontend on ONE PC in the house.

All PCs running Ubuntu 12.04 (I think? Did I upgrade the backend? Better check ... it might still be 11.10)

But the PC and laptop are both 12.04 64b and up to date.

Laptop works fine, PC doesn't. Have tried removing and purging Myth from the PC, removed the .mythbuntu and .mythtv folder from /home ... nothing. Can't get it working on my desktop any more. Can't even remember exactly what changed when it stopped working.