You said it yourself - the invitations have *started* to go out. They haven't finished going out yet!
Relax if you can (I can appreciate the anxiety of uncertainty), but it's still relatively early. You should be concerned if you don't hear anything by the Thanksgiving (but then again, HBS has been known to give out interview invites as late as mid- to late-Dec). Also, whether you get the invite early or late is no indication of where you stand - keep in mind that admissions offices are bureaucracies having to sort through a ton of paperwork, and they're just churning out decisions as best as they can.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com