Please refer to the attached sample project.
1. Run the application, Excel will be opened.
2. In the Add-ins tab, click button2. A form with a RadMenu will be shown.
3. Close Excel but leave the form opened. As a result Excel hangs.
Unfortunately, the issue is at a location that is too deep for any customization to have effect on it. Excel hangs when the you leave the form opened. Our RadMenu doesn't indicate any incorrect behavior. You should close the form before closing Excel.
Regards,