Today when I tried to run P7 it flashed to the gray screen as if it was about to start, then it disappeared.

The program will not run.

Nothing in the event viewer.  Tried various compatibility modes.  No luck.

I'm going to try to reinstall, but wonder if I can safely restore my current runtime.

If you can, backup your runtime before a new install.  Have you tried opening a pz3 file? Don't start p7, just open a pz3 file. That might get your p7 to work.

PZ3 is the same, a gray screen shows, the background window for Poser 7, then it goes away and nothing more happens.

Well... That sucks big time. Something has gotten corrupted.  It's probably re-install time. Just be sure to backup your original runtime.  Copy your entire runtime to somewhere else. Then un-install and re-install. Or perhaps you could try and contact Smith Micro before unistalling p7. But it really sounds to me that something has gone really wrong and a fresh install of P7 is needed.

Be sure you re-install to a NEW folder, not to the default or original folder.
The installer often fails to overwrite corrupted DLLs.

I installed to the original folder.  Everything works fine, I didn't even have to copy the backed up runtime.

Whatever the problem was, uninstalling and reinstalling in the same dir fixed it,

I guess I spoke too soon.  Poser runs but won't load or render any of the old files.  The textures library is gone from the Poser 7 runtime, including from copies made a long time ago.  I just checked a copy on a DVD made 2 months ago, even the textures library there is gone.

Up until yesterday I had used figures from the main runtime, including their textures.  No idea where the textures directory went, or how it could have disappeared even from old copies.

I had a similar problem with another program and it turned out my hard drive was going bad, run chkdsk and see if it finds bad sectors.

I'll do that, but it doesn't explain why the textures dir disappeared on DVDs and Hard Drives not connected to the PC, in storage.

I have Michael 3 completely installed in a external runtime.  I've loaded M3 from that runtime forever.  Apparently it uses the textures from the main runtime, because with them gone the M3 takes forever to render and/or load.

At least I can copy those textures over, but the thing is all the freebies I had installed.  It's going to be a long time downloading stuff to find the textures.

ARGH.

I feel your pain. My entire poser runtime went kaput 3 weeks a go. Everything I had ever done with poser in the last (oh lets say) 8 years, was washed away. Hard drive got a little bit destroyed.

Could be needing a restart? Isn't Poser a memory hog? Maybe shut down and restart to fix it. . . I am wondering if this will work for you.