glUniformMatrix GL_INVALID_OPERATION Error

JOGL Debug is reporting a GL_INVALID_OPERATION error when I'm trying to upload a FloatBuffer containing 4x4 matrix data to a shader uniform.  I can't figure out what the problem is?

Looking at the OpenGL C docs, GL_INVALID_OPERATION can be reported for quite a few reasons:
http://www.opengl.org/sdk/docs/man4/xhtml/glUniform.xml

The FloatBuffer is of size 16 floats, and I tested the actual computed matrix data (it's an ortho-projection matrix) in a mat4 constant on the vertex shader - it worked.  So, the problem is only occurring with the upload process.

I set the uniform matrix via the following call:

    gl.glUniformMatrix4fv(getLocation(name), 1, false, values); // values = the non-null, capacity 16,
                                                                                                          // zero position FloatBuffer

The getLocation(String) method is:

        private int getLocation(String uniform) {
                return gl.glGetUniformLocation(progId, uniform);
        }

The name variable is the mat4 uniform's name on the vertex shader.  It's declared in the shader as:

    uniform mat4 ortho;

And used as:

    gl_Position = ortho * pos; // where pos is a vec4 containing the passed vertex attribute

Any help is appreciated.  I really have no idea what's wrong :(

Edit: Addendum - Full error message:

GLDebugEvent[ id 0x502
        type Error
        severity High: dangerous undefined behavior
        source GL API
        msg GL_INVALID_OPERATION error generated. Uniform not found.
        when 1390875845182
        source 4.3 (Compat profile, arb, debug, ES2 compat, ES3 compat, FBO, hardware) - 4.3.0 NVIDIA 310.44 - hash 0x2e1c3062]

glGetError() returned the following error codes after a call to glUniformMatrix4fv(<int> 0x3E, <int> 0x1, <boolean> false, <java.nio.FloatBuffer> java.nio.DirectFloatBufferU[pos=0 lim=16 cap=16]): GL_INVALID_OPERATION ( 1282 0x502),

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Additional edit:

I just noticed that "Uniform not found" message.  I double checked.  The name being passed matches how it's declared in the vertex shader.  Do I have to do something to the buffer or method call to match the mat4 properly?

It looks right, the only difference from my code is that I use float[] instead of buffers but that shouldn't make a difference. Given the error description I would bet that it is a typo somewhere :-)

Is the shader linked without errors? Are you sure you actually pass in the correct programId? That's where I would start looking after checking the obvious things you already checked.

The shader does link without errors, and glGetUniformLocation returns a valid value for the location of the uniform specified by 'name'.  I can't find any typos.

The program id is correct.  It's the only one available in the class :)

I really have no idea.  Maybe I should just try using an array instead?

Or maybe you forgot to glUseProgram before you try to set the uniform value. That could be one cause.

jmaasing wrote

Or maybe you forgot to glUseProgram before you try to set the uniform value. That could be one cause.