Are they large PSD files? You may need to go to Edit>Preferences and put a bigger number in the box that says "Do Not Process Files Larger Than."
Well, thanks for the idea, but no, they're files I've worked on many times in the past, JPEGs, Tiff, even RAW files. Funny thing is, I shot some new photos and they show up fine. It's the older ones that have suddenly disappeared in Bridge. I've cleared the cache, even reinstalled. Still, can't see them. Weird.
Confession - I "lost" this message, i.e. forgot where I posted it, so I re-did it in Digital Image Processing, where it probably should have been all along. But no one seems that interested there, either.