Well, I'm on a PC... but in the Spark Library there should be a Factory and a User folder. In the User folder there would be the named project folder and inside that folder you should at least have a .dat file of the same name. You may also have a .png or .jpg image file, and if you chose "Save a copy of audio samples in library" in the preferences tab then you will also have an Audio folder. When I upgraded from Windows 7 to 8, it was as simple as just copying the same folder structure on the new machine. The only other thing I could say is to make sure that the Library path is also set correctly in the preferences tab.
If you create a brand new project/kit, are you able to reload it?
You could also export each project on the old machine and import them on the new.