I've been working with one particular Poser scene for the last week (4 figures and a room, nothing at all strenuous for my Mac). And until today, no problems. But suddenly after trying to save the file (after adding nothing to it), I got the attached message. I also had to force quit the program. Now, whenever I try and open that pz3 file, it doesn't open, I get the same error message and Poser locks up. Any suggestions?

Do you have a time machine backup of the PMD and scene file from before the crash happened? It might be worth restoring such a backup to a different folder and seeing if Poser will open that. Provided the PMD hadn't been significantly added to, you might be able to resurrect the scene with the backup PMD and the current scene file.

Good luck.

ADP wrote some python routines which can examine a PMD file and extract data from it. If you don't have a backup, unfortunately, the PMD may be corrupted beyond rescue. I could try and ask whether ADP is willing to share that python code, or else inspect the file myself, if you have sufficiently large cloud storage and bandwidth to share the file, that is. I think it would also be prudent to list which figures you have in the scene, so we can work out whether you're allowed to legally share any part of the scene. Otherwise someone at Rendo may be able to provide support in that regard.

No backup, unfortunately. This has happened to me before with other scenes, just not very often and usually with much larger scenes. Guess I should really start backing things up more often. Fortunately, I got pretty much everything I needed from that scene and may not need to recreate it. Thanks for your help.

Try turning off the PMD stuff....
It's in preferences... the check box is called use external morph targets.
But I use Windows, so this may note be helpful to you.

I have one conforming item I sometimes use that will cause that exact error every single time. The first time I save the scene with that object, it saves fine. But if I load the scene again after having shut down Poser and restarted, I will get that error message the next time I try to save that scene. I've tried downloading a fresh copy of the files, but the problem still persists, so I have no idea what's causing it.

Basically, when I get the error message, I just keep clicking on OK and it eventually saves. Then I turn off the PMD in preferences, save the scene again with a different name and no error message, then restart Poser. Open up the non-PMD saved file, turn on PMD, then save the scene again. Usually, that will correct the problem and stop giving the error message on a save. Sometimes it won't.

It's definitely an issue with the PMD. Saving the scene without PMD won't give the error message, but will give you a huge file.

So there you have it. The PMD is corrupt in some way.
If you insist on using PMD's (I'm NOT a fan!!) you can turn PMD's on again, after you create the good copy, and save
Maybe this PMD won't be corrupt.... BEST of luck to you!