Please check your MAPI configuration, the text below copied from the Personal Outlook Migration help.
There are well known MAPI configuration issues when running both the GroupWise client and Outlook on the same workstation. Prior to migration, prevent Outlook using the Novell MAPI default settings by configuring the Outlook client to prompt on startup for the MAPI profile to be used.
You can configure this behavior in the Outlook client under Options | Mail Services | Prompt for a profile to be used. On Windows 2000 or above, you can also set this option by using the Windows Control Panel | Mail | Show Profiles, “When starting Microsoft Outlook, use this profile:” Prompt for a profile to be used. When Outlook starts and prompts you for the profile, select the appropriate one to connect to your Outlook data.
Once the above MAPI configuration defined, start the Outlook client and review the address books. Close the Outlook client then start the GroupWise client.
Hope this helps.