I think my VS is drunk (2010 & 2012).
The symptoms
I open a particular project and I see some unresolved symbols. However, when I compile the project it builds succesfull and I can run it. in 2010 I can click on the unresolved symbols and it brings me to their declaration and implementation pages. (not in 2012) My intellisence also doesn't work on the symbols that are unresolved, it does work for all the rest.
I tried restarting VS, but to no avail.
I don't think adding more references is the answer, since the projects compiles and runs ok.
Extra info: I use Rescharper