OK - so I didn’t fully explain the Steinberg recommended method, which is copied here:
Re: Cubase VST Song import in Cubase 4/5: a solution
by Steinberg Service » Mon Jun 18, 2012 12:01 pm
Dear Cubase customers,
Cubase 4, 5, 6 and also 7 do not support the import of Cubase VST songs and projects anymore. In order to import your older Cubase VST projects and songs, you can install Cubase SX3 / SL3 / SE3, which are available as a download here:
Cubase SX 3
Cubase SL 3
Cubase SE 3
Cubase SX3 / SL3 / SE3 can be run with your current Cubase licenses and allows you to import VST projects, save them in the new *.cpr format and open them in current Cubase series. These are not officially supported under current Windows OS but should install and run just fine under Windows Vista / 7 / 8.
Please note that Cubase SX3 / SL3 / SE3 are PPC based versions and the latest Mac OS to run PPC applications is OS X 10.6. For Mac installations please be sure to install the eLicenser Control Center for Mac OS X 10.5 (PowerPC and Intel based), 10.6 and 10.7, which can be downloaded here.
My projects were created with VST 5. My issue is that when I try to import them into SL3, which I have downloaded, all projects are greyed out. I am working with OS 10.5, so according to Steinberg it should be compatible.