It's 2009 and Calendar Invites Don't Interoperate?

So I must be missing something big here, because it seems that this should not be an issue in 2009.  Susan is fully on a Mac using the iCal app.  When she sends me an invite, it shows up in Outlook on my end sort of looking like one, but when I click on the attached .ics file, the Accept, Reject, etc buttons are greyed out (for those of you wanting details, this is Outlook 2007, Service Pack 2 running under Parallels on a Mac).

I did a bunch of searching around without finding an easy solution.  There are a bunch of fairly obscure posts about hacking the iCal app to fix this.  I have also figured out the following insanely-ridiculous-but-still-slightly-better-than-manual-reentry way of getting the info into my calendar: launch IE under parallels and use OWA (outlook web access) to get to the message.  Then click on the .ics file while having Outlook running.  Choose “Open” in the file dialog box and voila the full accept and reject dialog is there.

My BlackBerry also does not like the invites generated by iCal.  They arrive with two attachments.  One is an html file which is empty, the other is shown as a “msg” file, which my BlackBerry refuses to open.

It’s not even that the underlying standards are in any way new.  iCalendar is RFC 2445 from 1998.  Maybe the standard allows for enough leeway for different implementations not to interoperate.  Still does not seem like the kind of thing that should be broken in 2009!