Yeah, I don't have a very good track record on them right now do I. Twice in less than a week. Portage based systems really don't like to be updated.
Anyway, I changed /etc/conf.d/xdm's display manager to kdm from xdm and it's working now. Only side effect is the kde login screen has replaced Sabayon's default one, but that's a minor detail. Thanks for help. I'll try not to clobber any more config files