Visual Studio throws error when I make a using directive for a project I referenced in my solution

My solution (this is VS2010 Express) contains three projects. One is my main project that uses Xna, the second is called MyExtendedContentProcessor, and the third is a blank class file identical to what you get when just add a new project (even called ClassLibrary1). My main project can reference ClassLibrary1 if I add the reference, but if I add the reference to MyExtendedContentProcessor, I can add a using directive, but then when I build I get

Error 1 The type or namespace name 'TriangleProcessorExtension' could not be found (are you missing a using directive or an assembly reference?)

And after that intellisense will no longer see the namespace inside MyExtendedContentProcessor. I'm really not sure why it is acting this way. By the way, if I comment everything out of MyExtendedContentProcessor, it still does not let me add a reference to it.

Any help will be appreciated.

EDIT: (Taken from my comment) Also, not sure if this is related or not, but I'm unable to change my output path. I can change it, but it doesn't actually change where the files are being copied to, and if I restart Visual Studio, the build path is the same as it开发者_StackOverflow was before I changed it (even though I pressed save)