Sadly I have no idea what's causing the problem and I can't reproduce it. I have a feeling you may have a program installed that's interfering with .Net in some way.
As to adding the macro by hand:
This editor only edits the 1-5 buttons in the Group/Raid window. Not the 'click to cure' buttons. If you want to add the Cure Curse to 1-5 buttons here are the instructions:
http://gm9.eq2interface.com/portal.p...a=faq&faqid=35
If you want to edit the 'click to cure' buttons I'm sure there are instructions somewhere (I've never used them)