Podcast entry grayed-out, yet downloaded.

This is new: in iTunes I have a couple of podcast entries that have been downloaded (I can see the corresponding mp3 files on the disk) and marked as un-played, but they are grayed-out and unchecked.
I can't play the tracks, I can't select them and they are not being synchronized to my iPod either!

(Update: restarting iTunes made the grayed-out files available again. Duh!)