>Ok, I put thisform.gridname.recordsource = tablename in the form init event. Now finally the form is showing data! That's some progress. BUT it is the wrong data! This makes me think that the record source gets changed somehow when the form is opening. How do I determine what the record source is at any one point so I can figure out what is going on?

You should try following literal commands:
***Form.Init event
With This.Mygrid
.recordsource="mytable"
.columncount=1
.column1.controlsource="mytable.field1"
.refresh
Endwith