Importin Wav-files. Speed up the file.

Hey there.
I use Cubase 5 to start with.

And to my problem;
I’m a vocalartist and I mix the tracks but when I import Wav-files Cubase automaticly speed up the instrumental, only the instrumental, do not effect the other stuff in the project. I have no idea why it does this and it’s really annoying.

Someone experience the same thing or know why and how to resolve this?

Sample rate mis-match.