Problem with creating list box or other controls

I have created numerous worksheets with list boxes controls in MathCAD 13.  Now, when trying to open those worksheets in MathCAD 14 the list boxes do not work and a message "Value cannot be null.  Parameter name: pUnk".  Same thing happens when reviewing examples from Quicksheets or other downloaded example worksheets from the internet.  I do not seem to recall that I was ever able to open and execute a list box after upgrading to MathCAD 14.  Also, when trying to Insert -- Control -- List Box (or any other control) ... nothing happens.  Any idea on how to make the list boxes (and the other controls) work again?  Thanks for your help