I went straight from 5 to 7 and I believe some new nodes were added to the material room (I could be wrong though)

Posers search makes testing file references quite difficult , so its worth looking at any long load times to see if its pointing at the right place.

If there is a png or rsr thumbnail in the folder it should display but you may need to edit the file in poser 5 folder that limits thumbs to 100 items.  Thats Libraryprefs.xml in runtime/prefs folder .

<LibraryPreferences curFolder="2"  previewNum="100" >   this line change 100 to 500 and see if your thumbnails appear.

To follow up on inj/rem poses or mat poses would need an example.