The following topics are known upgrade issues.
FlexGrid - Upgrade to Version 2.6.20102 (.NET 2 / 3.5 Versions)
The Grid Property of .Refresh = <True | False> which controlled the automatic redraw of the grid cells has been replaced by two new Grid Methods: .BeginUpdate() and .EndUpdate(). Use these methods to prevent continuous redrawing actions as the grid structure is changed / rows populated.