js script suddenly not found by c# scripts

I have a c# script that uses CharacterMotor which have been working fine for a while.

Suddenly I got the error message:

 Assets/Scripts/WalkingSound.cs(9,17): error CS0246: The type or namespace name `CharacterMotor' could not be found. Are you missing a using directive or an assembly reference?

I have verified that I do indeed have a CharacterMotor.js file in my project. I tried restarting unity, but had no luck with that. I could check out an earlier version of my project, but it's been a while since I last commited, so I wish to avoid that.

Any suggestions?

EDIT: I'm also positive that CharacterMotors.js is compiled since I can edit it and make some errors and unity will show them in the console.