Outlook 2k3 user cannot open Outlook 97

First,we are unable to upgrade all systems to Outlook 2k3 yet. We still have Win98 users on Outlook 97. Problem is a user that has used Outlook 2k3 is not able to open Outlook 97. Error message says a fault has ocurred in unknown module with a memory address. Previous research says the Cached Mode operation setting needs to be turned off. Did that on a previous user, but on this new user, it doesn’t work. Any suggestions on what to do.