Can you create a new scene with M4 and save it? Also, where are your items saved to? Try creating a folder under my documents, call the new folder Test Renders, move the saved m4s to there. Do all this with poser closed. Open poser and try to import from that location.  If it works, store the new scenes there. I'm thinking it could be a directory permission change. Also check your firewall settings. Poser tends to want to use shared directories (not shared with everyone, just your local home network). A firewall update could have changed these settings. You might have to check the folder permissions.

The dust settled, thinking "what a fine home, at least for now" not realizing that doom would soon be coming in the form of a vacuum cleaner.