eclipse mars.2 on mac os 10.7 seam runtime doesn't exists in project properties and my project gives "Seam Runtime "xxx" specified for Seam project "yyy" does not exist " problem.
is it about you or ??
Please go to Preferences -> Seam and make sure the Seam runtime is defined there. Then go to Project properties page of your project and make sure all Seam properties are correct.