Oops, Premiere Pro CS 6 for PC running 64 bit Windows 7. I always forget that.
I had videos from two sources in my project, one taken with my Canon D60 (or similar) in .mov and one from a different .mov. I did a lot of my editing, saved it, and the film from the canon was just black, but still had audio, and the generic footage showed perfectly. But the camera footage still appeared in the bin, so I right clicked and replaced with footage from bin, but that replaced the footage at the beginning, getting rid of all my edits. It did work though, and brought back the video.
The only thing that I did in between saves was import an Adobe Illustrator file, but I’ve never had problems with that before.
Thankfully, I pathologically save all the time, with new names, so I had a very recent working backup (all of my backups had the video correctly showing). But I can’t figure out why it did that.