Copy and Paste (Command C & V) into Dialog with Custom Menubar - No longer works

I'm updating a standalone app into Max 6 for the first time and the one thing I've noticed that used to work but no longer does is is copying and pasting into a dialog text field. This is an important part of my application and not being able to use the command c and v macros is a pain.

To reproduce create a dialog object and a menuitem object that loads by default, build it into a stand alone, try copying and pasting a line of text from an email into the dialog. It just creates an alert sound. It's possible (and not at all convenient) to drag highlighted text to the box, but this is not a satisfactory work around.

Can anyone advise? Is this just something that is now disabled by default but can be re-enabled? It worked fine in Max 5.