freehand mx 11 install problem

Hi
Here's the problem, I'm trying to help a person install freehand mx 11 over the phone and they are not real computer knowledgeable.
Here's what they said
It's a new product came in shrinkwrapped box.
They are running xp, when getting to the part of install freehand that requires the serial number, they put in the number but there is a "NEXT" button that won't highlight to let them click to proceed. No messages show up, they just can't go any further because the button is dead.

Do they have to be online for the "NEXT" button to highlight and let them proceed?
Does the number have to be correct before the NEXT button will highlight?
Are letters (if any) that are in the serial number case sensitive?
What else could cause the button not to highlight?

Thanks
Frank