I've opened many files from Version 5.2 in Sonar Pro. I don't think there would be any inherent issue coming from 5.0.1 One thing to look for is the opening file dialogue - I often have a number of plugs that are no longer installed as well buss assignments that don't conform to my current interface. If your files are opening but just not " playing back " then I suggest you solo a single track and go through its routing to see if you find your current set-up is not routing correctly.