I have found that if I leave MythTV frontend open to the menu screen for any extended period of time, the guide data somehow gets deleted, and I am left with 'unknown' for every channel (regardless of tuner). When this happens and I try to edit/look at the channel info (via frontend channel editor), it looks like all the values get stuck on 'loading . . . ' and never come out. Usually a run of mythfilldatabase (which seems to be taking forever lately!) fixes the issue, but not the past couple of times. If Myth is left in LiveTV mode, this doesn't happen, but I don't think I want my processor and hard drive constantly working, even when I am not watching TV.

Any thoughts on what is deleting my guide data?

I've never heard of that.. you may want to send an email to the mythtv-users list

Yeah, it is a weird one. I think the guide data it there, it seems like Myth forgets what the channels are and therefore doesn't know what to put in the database? Is this possible, or is mysql linked to the backend, such that the frotend forgetting the label of a channel should have no effect on guide data?

What's your mythfrontend log say (/var/log/mythtv/mythfrontend.log usually)? Anything funny?