glDrawArrays - Getting GL_INVALID_OPERATION and GL_INVALID_VALUE

Question

I am porting some legacy OpenGL code to Web Assembly (using emscripten). This is using OpenGL 1.1

I have two vertex formats, and I swap between them (depending on whether I'm doing 2D drawing or 3D drawing). Here are the two formats:

struct Vertex2DRef
{
    float           mX;
    float           mY;
    float           mZ;
    unsigned int    mDiffuse;
    float           mTextureU;
    float           mTextureV;
};

struct Vertex2DNRef
{
    float           mX;
    float           mY;
    float           mZ;
    float           mNX;
    float           mNY;
    float           mNZ;
    float           mTextureU;
    float           mTextureV;
};

This is old, legacy code, so I'm just drawing straight from memory buffers. When I'm drawing 2D, I do this (Don't mind the XGL wrapping, it's just a define to also report if the call is producing errors):

        XGL(glEnableClientState(GL_VERTEX_ARRAY));
        XGL(glEnableClientState(GL_COLOR_ARRAY));
        XGL(glEnableClientState(GL_TEXTURE_COORD_ARRAY));
        XGL(glDisableClientState(GL_NORMAL_ARRAY));
        
        int aStride=sizeof(Vertex2DRef);
        Vertex2DRef* theRef=(Vertex2DRef*)theBuffer; // <- The incoming vertices are in "theBuffer"
        
        XGL(glVertexPointer(3,GL_FLOAT,aStride,&theRef->mX));
        XGL(glNormalPointer(GL_FLOAT,aStride,NULL));
        XGL(glColorPointer(4,GL_UNSIGNED_BYTE,aStride,&theRef->mDiffuse));
        XGL(glTexCoordPointer(2,GL_FLOAT,aStride,&theRef->mTextureU));
        XGL(glDrawArrays(GL_TRIANGLES,0,theTriangleCount*3));

So the above works... I get my render exactly as I expect them.

HOWEVER: When I try to draw the other vertex format, the one with normals, but no diffuse:

        XGL(glEnableClientState(GL_VERTEX_ARRAY));
        XGL(glDisableClientState(GL_COLOR_ARRAY));
        XGL(glEnableClientState(GL_TEXTURE_COORD_ARRAY));
        XGL(glEnableClientState(GL_NORMAL_ARRAY));
        
        int aStride=sizeof(Vertex2DNRef);
        Vertex2DNRef* theRef=(Vertex2DNRef*)theBuffer;

        XGL(glVertexPointer(3,GL_FLOAT,aStride,&theRef->mX));
        XGL(glNormalPointer(GL_FLOAT,aStride,&theRef->mNX)  );
        XGL(glColorPointer(4,GL_UNSIGNED_BYTE,aStride,NULL));
        XGL(glTexCoordPointer(2,GL_FLOAT,aStride,&theRef->mTextureU));

        XGL(glDrawArrays(GL_TRIANGLES,0,theTriangleCount*3))

Now, I get nothing at all. That glDrawArrays line drops two errors-- GL_INVALID_OPERATION and GL_INVALID_VALUE. The reasons the documents list for those possible errors don't even apply (confirmed that theTriangleCount is not negative, and I don't use glBegin or glEnd anywhere in the program at all.

Can anyone help?