Meeting invite missing from Calendar

In our company we are experiencing the following problem:

A user creates a meeting invitation and sends it out to a group. The intendees accept the meeting some via OWA some via Outlook 2007. Later, when they logon to outlook the meeting invite is missing from all of the intended users calendar.

I found an article here but its not very helpful: http://support.microsoft.com/kb/2222377

We run a mixed exchange environment 2003 and 2010. As far as I can tell all the users who are having this issue are still on the exchange 2003 using outlook 2007.

Id appreciate any help if anyone has experienced this and knows a resolution.

Thomas

Thomas