I've been tracking this but haven't found a fix yet. There is sometimes a beachball if you interact with the menu item immediately after launch. I'll keep looking.
FWIW, Mac dev. here too, seeing the same issue in 10.9 with my app (beachball when interacting immediately after launch.) Haven't been able to track this down yet.
Thanks, good to know it's not just me. The stack trace says "Carbon" a lot, hmm.