[EDIT]
In webgl/chrome, I get this:
ERROR: 0:4: 'ma' : arrays may not be declared constant since they cannot be initialized
ERROR: 0:4: '=' : syntax error
It doesn't look good.
Possibly related: How to define constant array in GLSL (OpenGL ES 2.0)?
Desktop GL...
Your code works for me, however I get this without setting a version:
warning C7551: OpenGL first class arrays require #version 120
Can you provide a #version
string in RenderMonkey?
I doubt this is the case but a really old card or drivers may be a factor.
I don't think you need the second 2
either: const mat2 ma[2] = mat2[](...
is fine