Same story here, amazing and pitiful. Since it was a couple of months old, I had the disappearing EPG often, commonly on the first weekend of every month, suggesting it was triggered by some periodic update. I just put up with it and learned to reset. But as with the previous posters, once the ads started showing up the disappearing EPG problem went away. I thought the problem had been fixed, and everything was fine and dandy in Pleasantville.
But now I'm getting the same timer rdy problem, with recordings starting a half hour late. I'd rather be forced to reset monthly than to lose programs, especially since Stargate SG-1 has some dynamite shows leading up to the end of the series, and Heroes is back. I've been getting 29 minute recordings, which means it's starting 31 minutes late. I don't think it matters whether the recording is set to start on time or a few minutes early.
I'm going to clean out my recording list, which is large, dump important stuff to DVD, then try compacting the disk, and last resort is to try a reset. If that doesn't fix it, I may just have to set up one long, manual recording for tonight. I won't be able to play music on hold with Pioneer until next week, but I'll pay attention to this forum and post anything I find out.
Aside: I really think this new problem deserves a thread of its own. It's difficult enough to search here, but limiting the search to titles helps a lot - if the title matches the thread. I'm glad I decided to check out this thread anyway, but not everyone will.