This happened to me too. If Im not mistaken, there's a switch (like a lever) on the right side of the camera, between the crank and the back. Flip that to the other position. use your already ruined film and rewind it. Load your back and try it. If that doesn't work, try it again and flip that lever to where it was in the first place. Load your already ruined film and try again.
If worse comes to worst, I've uploaded the manual as a pdf for you. Dead Link Removed.
Good luck to you on this.