Unable to get the window handle for the 'AxMSFlexGrid' control

Hi group,

I have this exception:
"Object reference not set to an instance of an object." and the err.Description contains this text: "Unable to get the window handle for the 'AxMSFlexGrid' control. Windowless ActiveX controls are not supported." when I close my application. I use MSFlexGrid in one of my forms inside a User control .vb file in the same project.

The marker points to

Public Class frmTestEditor

I get this exception when closing the application by pressing the X box on the top-right corner. If I use Me.Close it's OK - no errors and

What can be done?

Miroslav St. Jeliaskoff