Any more specific ideas Jhieminga?
Not really. I don't have an installation available to test my theory so I can't help you any further. I did a Google search on 'Outlook data file' which turned up some interesting reading, this page for example:
http://www.slipstick.com/config/defaultpst.htm
First try to set the Outlook data file for one user account to a location accessible to both (
http://office.microsoft.com/en-us/ou...124801033.aspx). Then go to the second user account and point Outlook to the same location (see above). That's my theory but you'll have to test it yourself to see if it's correct. Please make backups of everything first to avoid disaster!