Interesting. It does seem Poser-related. My Poser preferences are on the C: drive, but my Poser files are on the D: drive. If it was a bad drive or a Windows problem, I would not expect both to be affected (and not any other program).

The log file shows the Poser can't find the sim files for dynamic cloth items in the files. Ugh, I wonder if this means I've have this problem with any file I saved with dynamic hair or clothing.

I seem to recall having this problem before. Deleting the sim files fixed it, though you'd have to run the sims again. That doesn't seem to work this time. Sigh.