Excel Error: Error 800a0011 When Trying to Add a Control to UserForm

When adding a form control to a UserForm you might get the following error message:

Excel could not complete the operation due to error 800a0011

When this occurs, your VBA code is most likely currently in break mode.

Click OK in the error dialog and reset your VBA Editor (Run->Reset). Now you can add the form control to your UserForm.

Works at least for Excel 2007.