Element undefined in URL CF11 worked in CF9

We recently upgraded from CF9 to CF11.  I am having an issue where CF is throwing Element undefined in URL when the variable is clearly defined in the URL. Here's the flow...

The user clicks an icon to update an item.  A new window is opened and variables are passed in the URL.  User makes the changes, presses submit, CF makes the updates then the Window closes.  This worked fine in CF9.  Since the update when the user presses submit the window never closes and CF throws the error.  Nothing changed in the code.

Thanks in advance for any help!

Gary