A client recently asked: When I have the Outlook client open and open the web client the Customization option does not appear? Is there a fix for this?
This has been how MSCRM works for quite some time and is not considered an issue by Microsoft so it will most likely remain this way.
There is a workaround. Open the web client using the IP address and open the Outlook client using the server address. This gives each client a different cookie and the problem goes away.