I think I fixed this on my own. I had a rule set up in Outlook that cc'd
every email I sent to my email account, including meeting requests. It meant
every time I sent a meeting request it added me as a participant for the
meeting as well as the meeting organizer. Then when I accepted the meeting
request to keep it on my calendar I became a participant only and could no
longer make updates to the item. I solved this by modifying the rule to not
copy meeting requests back to myself. All seems to be well now.

"MB68" wrote:

I am using Outlook 2003 (Office Professional w/SP2), and for several months
now, each time I update a meeting request that I originally created, it is
deleted from my calendar when I send out the update UNLESS I accept the
update to my own meeting request. However, then it makes me a participant
and no longer the meeting organizer and I can make no further updates to that
meeting request.