I exported individual tracks of my project onto my desktop as wav files. When I imported them into a new (empty) Cubase project, they sound slower and in a lower key. The way I imported them into the new project was by just grabbing all of them from the desktop into the new project. Then it asked me if I wanted them on one track or separate. Everything was lined up right, but like I said, wrong tempo and wrong key! Please tell me what I did wrong. By the way, if I would have put them into the same project, maybe this would not have happened? Thanks a lot. 
Check for samplerate mis-match.
Thank-you.