I open INVDTAIL(and all other tables) in a main menu's valid snippet, just before the form is called.

Interesting! I just added a field from INVDTAIL to the form as a text box and set its ControlSource to INVDTAIL.ItemCode (same source as grid's column 1). I CAN edit this field. I also had added a ThisForm.PageFrame1.Page1.Details.refresh to the valid snippet of this text - and indeed the grid refreshes. PLUS, I can edit records in the grid. BUT, if I remove the text box field from the form/page, I go back to not being able to edit in the grid. We're close here, I can smell it :) But I'm not sure what to check next?