GLSL w/ glPolygonMode(..., GL_LINE)

OpenGL OpenGL: Basic Coding
1

When I run the following code, my first pass GL_LINES is drawn as solid instead of wireframe. I don’t get it. I’m using VBOs and GLSL shaders for processing. The second call (Fill) works as intended. I’m using NVIDIA QUADRO FX 1800 - does anyone know what I’m diong wrong?

		glCullFace(GL_BACK);
		glEnable(GL_CULL_FACE);
		glEnableClientState(GL_VERTEX_ARRAY);
		_shader.bind();

		glFrontFace(GL_CCW);
		glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
		glDrawElements(GL_TRIANGLES, _indexCount, GL_UNSIGNED_INT, 0);

		glFrontFace(GL_CW);
		glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
		glDrawElements(GL_TRIANGLES, _indexCount, GL_UNSIGNED_INT, 0);

		_shader.release();
		glDisableClientState(GL_VERTEX_ARRAY);