JTalton has uncovered some errors in the OpenTK.Math.Matrix4 implementation. Specifically, the Frustrum, Perspective, Rotate, RotateX, and Multiply methods return incorrect results.
Attached is the program used to test these functions, kindly povided by JTalton. Note that the multiply test may be wrong, so don't rely on its results.
Please use the equivalent Glu methods until the OpenTK 0.3.14 release.