Well, it took 20 minutes, but I figured it out.
I had taken a grid that was using ObjectDataSource and replaced it with the LLBLGenProDataSource. When I started with a brand new grid and hooked everything up, it worked.
The problem is, it had the DataKeyNames field set to 'FieldNameID' from the objectdatasource....as you know, LLBLGen names that field 'FieldNameId'.
Once I spotted that and corrected the case, it worked!!
(Note, before I posted this, I did start with a new RadGrid - but I also forgot to turn on the automatic updating.....whoops....)
Thanks Pandu!