At least it seems to be DST related. Here's the situation:

I have two machines: one is a backend/frontend running R5C7, one is a remote frontend only, running R5D1. (I know, I know, I'll upgrade when the next revision comes out.)

I applied the Daylight Saving fix to the backend, but not to the frontend, figuring "hey, it's a remote frontend, the backend is what's important."

Yesterday I checked my backend machine to make sure the time was correct, and it was.

This morning, I saw that it had recorded a Sunday night show (post-DST shift) at the proper time. I started playing the show back from the frontend and all seemed fine... until I tried to skip forward 30 seconds. It took a second or two to do the skip (normally instantaneous) and when it finally skipped, the picture was corrupted and took a few seconds to clean up and start proper playback. Moreover, I was unable to skip forward 10 minutes (playback just stalled altogether) and I was unable to store a bookmark (playback always started from the beginning of the file).

All other shows that recorded before the DST shift played back fine from the remote frontend.

I tried playing back the post-DST recording from my backend machine... and everything worked fine: skipping, bookmarking, all was fine.

I've applied the DST fix to the remote frontend but haven't had a chance to check if that's fixed the playback problem. It's just strange that having the remote frontend's time being off like that would cause this behavior, if in fact that's what's going on.