I am experiencing the same problem.
I have a user editable check-column with filter. The name of the column is "include".
The intention is that the user can selectively identify rows to be included in the output. But when I attempt to programatically set or reset all of these records while the gridview filter is in place.
when I set the filter (checked or unchecked) and thereby impose a filter, I get the error when executing this code:
foreach (var childRow in radGridViewWells.ChildRows.Where(r => r.IsVisible))
childRow.Cells["include"].Value = false;