The attached ICS doesn't seem to be parsed correctly. It just offers to save it to disk.
Can you attach the file, please? ;)
It's here: http://www.gnome.org/~jrb/files/invite.ics
I just tried to import this file to evolution 2.24.3 and it offers me an iCalendar file type, but, because you are talking about Save as, I believe you are doing quite different thing, probably part of some message? I would suggest two things: a) check whether itip-formatter plugin is turned on in Edit->Plugins (event if it isn't it should show some sort of invitations), and also look in which state is your prefer-plain plugin, as well as in Edit->Plugins, then also in Edit->Preferences->Mail Preferences, tab HTML Mails b) is it possible to upload here that mail message?
Oh, thought it had attached when I submitted it. Sorry. It is attached to a message I received, and I have attached the full message. The itip-formatter plugin is turned on. I have "Show HTML if available" set as well.
Created attachment 332411 [details] mail message
evolution-2.24.3-1.fc10 doesn't contain patch from the upstream bug [1], whereas evolution-2.24.4-1.fc10 does. You can disable prefer plain plugin (or just move it to any other option than "Show HTML") and it'll start work. [1] http://bugzilla.gnome.org/show_bug.cgi?id=567687