Hi,
I manage a network running SBS2003 with 30 XP Pro clients running Office 2007. Back in December 2010 user1 sent out a meeting request to User2. User2 accepted the request & User1 received the response.
Since then User2 has been automatically sending out the same reply to User1, several times a day. By automatically I mean that the user is not sending the reply, but Outlook is automatically sending out the reply. I have seen it send a reply whilst connected to the client by RDP & there are dozens of reply's in the "sent items" folder of User2.
There is no pattern to the sent replies, sometimes minutes in between & sometimes hours. The replies stop being sent when Outlook is turned off.
I have tried the following,

I have accepted the original request again.
I have deleted the original request & the calendar entry that it created.
I have scanned the .OST file with the scanost.exe tool.
What could be causing this?

Do you use exchange or a third party ISP and pop3 e-mail? If your using an ISP just delete it from the server.

I've seen a corrupt ost cause this in the past as the e-mail flag never shows as "read" so outlook thinks it has a new e-mail it needs to reply to on every send / receive. Even after a scan it would still do it so I was able to fix that and a few other odd problems by creating a new ost and moving all the data to the new file.

I have tried this & created a new profile, but still the reply is generated.

Same thing i want to know, there is an connection error or something else.