Remove focus from dialog cancel button

Hi folks, I have created a plugin that integrates the (truly) WYSIWYG MathDox formula editor with CKEditor. Here's a screenshot:

But do you notice how the Cancel button is focused? That means that you can click to insert typeset math, but as soon as you press the space button, instead of inserting a space in the MathDox editor, you activate the Cancel link and the dialog diappears!

Can somebody tell me how to move or remove the focus from the Cancel button?

As a workaround, I might implement an alert like "Are you sure you don't want to save your formula?", but I'd rather fix the problem outright than code arond it.

Thanks to everybody on the CKEditor team for their hard work! I'll try to open source this plugin but I'll have to clear it with my client first.