I'm not sure why that's causing an error, but I'm undergoing a pretty huge cleanup and beef-up of the launcher right now. If you have feature requests or bugs to report, I'm trying to keep them somewhat consolidated at
http://speedofmac.com/blog/speedofmac-mp64-launcher-feature-request/, but I'll try to remember them if you give them to me some other way.
In the meantime, here are some things to look forward to when I release the new version of the launcher in a few days:
New save state browser with the ability to delete
and launch save states (this will take a bit of work, so I'd call the save state launching a beta feature for now. It is working for some game titles already, though)
Save state backup feature
Cleaner and more concise AppleScript code
Improved preferences (replaced buttons with checkboxes where appropriate; more preferences saved between sessions)
Pressing 'Return' opens the selected rom in the rom browser
New icon:
I'm pretty excited about this upgrade, and I hope that it cures more headaches than it solves!