I recently installed Platinum 32 bit. Since then, when I open SPlat 64 bit I first get a pop-up that says: "Sonar will now personalize your user settings by copying application data files. This may take a few moments. Click OK to continue or Cancel to abort the personalization."
 
I'm always a little nervous when something like this shows up when it hadn't before. Is this supposed to happen? Is it alright to click OK?

Yeah, Sonar has done that for years. It just makes most settings the same as your previous install, to make things as similar as possible.

This is a normal popup when an individual user runs Sonar (or Music Creator) for the first time after an upgrade or a patch.