That's right. A saved scene can not be re-opened. To turn off PMD's open Edit > Preferences on the Misc tab uncheck "Use External Binary Morphs"

Scenes will save and load slower and take more space BUT at least they will re-open.

Also if you have a scene that is fried this way go find the PMD file and delete (or better yet rename it) the scene will open with no morphs. Now you can save the poses for your figures that will make recreating the scene much easier.

Be sure to exit and restart Poser after recovering a scene this way. We don't know what is causing the corruption and you may accidentally save the newly created scene in a broken state.