EP 2009 axGridView error after line selection

[arnold]

Thanks for the answer buddy.

But the real problem was in DataKeyNames property. I didn't specify one of the fields for the record to be uniquely identified, also it stated clearly in the Help.

More over the problem appears to be much complex with 3 joined data sources on the same user control. 3rd gridView should be placed within the ax form control otherwise selection of the line will cause disappearing of the grid without errors. I cannot manage to make the lines editable (grid is disappearing) but at least I can select and delete lines.
If somebody managed to make 3 level grid join editable on the 3rd level please respond.