wgl extensions deals with opengl, if you have a pretty recent pc than it just means you probably need a driver update which may fix it but if its an older pc, a driver update may still not be enough in which case you should look into another plugin for video.
It means your GPU doesn't support that OpenGL extension.
Either disable shaders within the plug-in, or better yet, if this is what I think it is, using Pete's OpenGL on a PC with an onboard video is a bad idea. Try the OpenGL (1) version of the plug-in. If that's too slow, try Direct3D or software plug-ins.