I know that there have been many posts about .ics files not getting automatically added to you iCal. I just upgraded from 10.6 to 10.8 and like the new mail app. However, my .ics invites are no longer be added to iCal automatically. Yes everything is set as it should be in both iCal and Mail for this to happen.
What I am wondering is if it is a problem with my main Email in Gmail. I have a verylongemail for my main Email on Gmail and can't change it because Google doesn't let you even when you are a paid subscriber. I didn't realize the long Email was such a pain until having to use it to log into things on an iPhone. I added an alias so that I now mostly use a short@ email which is nicer for clients too. However, I am stuck with my main long email address for account identificiation. So I wonder if that is the problem with ics files not getting added automatically. In iCal I can only specify one Email address for my Gmail account but in Mail I can add additional emails and have. But I think that ical and mail are probably not understanding that my short Email address is just as important as my long Email address in regards to adding invites to my iCal.