I've got a site I built from scratch on 2.1 and their time profile doesn't appear to be kicking in on time either - seems to be 5 or 10 minutes later either way.
I may have fixed it by deleting the profile from the hunt group entry, deleting the actual profile, rebooting the box, and then adding a new time profile and adding it to the hunt group again.
I haven't received a call from the client....yet!