Think I found it... I finally coaxed a different error message out of PPP - "Can't find required Bump Map..." Rebooted & reloaded the full scene, checked in the Bum Map list, then did a search on each. Found where 2 of the robots loaded without error, but the required Bump Maps weren't there. (1 from FreeStuff, one from a commercial product that was refering to a folder on drive E: (my drive E: is a Smartcard slot). I went thru one of the preliminary PZ3 with WordPad and deleted all reference to bump maps, and now the scene finally renders. Working on the full PZ3 now. Don't know how the CR2's loaded without errors, but if PPP had a better system of error messaging it would have saved me 3 days of tedious trial-and-error. Thanks for all the suggestions, everybody. sigh