In our last episode, I was re-downloading all my purchases. You'll recall my music had been playing correctly, but I wasn't able to get my various video files to play (e.g. "Tin Toy", "Thriller", et al).
The newly downloaded video files claim not to be authorized on my mac. I've backed them up, restored the backup on this PC, they seem to play fine. (Although, my copy of "The Final Countdown" music video seems to be corrupt, playing with a 4-color palette for some reason.)
I submitted yet another web "email" support request, giving them my gmail account name. This time, the automated response actually showed up (20 minutes later). (Aside: if I'm filling in a web form on your website, it's not really email, is it? I'd much prefer to use my email client where I can stretch out the window to a legible size and BCC myself so I can keep a copy for my records. Your web form doesn't do that, so maybe you should think of another name for the page other than "email tech support".)
Oh, and somewhere along the line, one of my manual syncs of the iPod trashed the entire contents of the device. I probably approved this wanton destruction as a side effect of some ambiguously-worded dialog box. Fortunately (?) most of what I've lost at this point is my play history, so I get to go back and listen to all my podcasts again.