Names.nsf does not exist

I am upgrading the my clients from 5.0.10 to 6.5.1. Two users have reports the following error when opening Notes. “names.nsf does not exist”. I rerunning the silent install over the clients and the problem seems to be resolved. What would cause this error?

I am using the InstallShield Tuner for Lotus Notes to create an automated silent install.

Thanks, B