When a user tries to start a program that was installed via a MSI package, the package is reinstalled?

If the user has a roaming profile, and the Delete cached copies of roaming profiles policy is enabled, this condition can occur.

When the cached copy of the profile is deleted, the %UserProfile%\Local Settings\Application Data\Microsoft\Windows\Userclass.dat file is deleted because the Local Settings folder is listed in the exclusion list for roaming profiles.

To resolve this issue, remove the Local Settings folder from the Exclude directories in roaming profiles policy.

NOTE: You can remove the Local Settings data value from HKEY_CURRENT_USER\software\Microsoft\Windows NT\Current version\winlogon\ExcludeProfileDirs. This will cause Userclass.dat to roam with the user.