if you are on windows, you really need to update your drivers then
GL_ENV_COMBINE is one of the OLDEST extensions to the OpenGL language in existence. and microsoft of all OS providers, provide really horrible built in OpenGL support, so you really have to use those provided by the OEMs (ie, ati, nvidia, intel, etc).
when you start up sandbox, you should also see 3 lines like this in the terminal, include them

Renderer: GeForce 9600 GT/PCI/SSE2 (NVIDIA Corporation)
Driver: 2.1.2 NVIDIA 173.08
Rendering using the OpenGL 1.5 GLSL shader path.