Another Can't Create Objects

I have VB6 and Crystal 8.5. I want to upgrade my users to Crystal9.0. However, If I uninstall 8.5 and install 9.0, I get a Can't Create OCX (or VBX) Object when I try to run a report. If I reinstall 8.5, everything is OK. So, for one user (my guinea pig) I have 9.0 and 8.5 installed. Do I need to install 9.0 on all the users PCs first, then my development PC, compile a new version of the application with the 9.0 installed, and THEN uninstall 8.5 from their PCs?
Anybody been through this?