Forgive what may be a naive question, but my in-depth experience with Cubase is quite limited.
I recently upgraded my system from a 2007 Macbook (Mac OS 10.7) with Cubase 6.5.4 Artist to a 2013 Macbook Pro (Mac OS 10.8) with Cubase 6.5.4. I used the Mac OS Migration Assistant to move all of my data files, including all Cubase projects, across to the new system. This seemed to work without a hitch.
Now, strangely, some projects - but not all - appear to playback at something less than full tempo (the ‘45rpm at 33rpm’ effect in case anyone remembers). After some analysis, it appears only to be those projects that had a history of first being laid down under Cubase 4 (ages ago). Recent works started under Cubase 6 or 6.5 appear to playback OK.
Project tempo settings seem to be OK.