So how many different versions of Dimension Pro do you find installed on the machine? You can find out by using Windows file system searches against "dimension*.*" for each hard drive.
Next, how many different "Multisample" folders do you find installed on the machine? Again, you can find out by using Windows file system searches but against "multisampes" for each hard drive.
Different versions of Dimension Pro (1.2 vs 1.5 vs 32bit vs 64bit, etc.) use different registry keys and possibly different file system paths. If there are multiple versions installed then you could be trying to use one version but the installer loaded the files into a Multisample folder for a different version. And the registry entries you're using to confirm might not be for the version that is being run in SONAR.
If there are multiple versions and multiple Multisample paths then this could explain the problem. Maybe getting rid of all of them then re-installing only what you want would be an easy way to remedy the problem.