It's not an Attmode problem.
I've narrowed it down via the suggestion of a friend that ithe problem might be caused by an Anonymous Block, which it is, and it was apparantly created either by a dwg crash, or during a Copyclip/Paste operation...but that's as far as I've gotten.
All I know is although purging alone does not fix the problem, I can copyclip the DB's out, purge the associated Anonymous Blocks out of the dwg, paste the DB's back in, and it prints fine.
Go figure...