Meeting requests seem to come in and Outlook claims that there is no organizer in the email section (as well as no accept/decline buttons). If you co to the calendar and open the meeting, you have the option to accept, and it claims that you cannot accept a meeting to which you are the organizer (these requests were sent by somebody else).
This has seemed to happen for all of my 2007 users. I have since downgraded them back to 2003, but wanted to know if you guys knew about this.
I may have switched the reported organizer in my description, as it has been a week or so since I had to deal with it. This happened in both the 4.5.3 and 4.5.4 clients.