I just fired up blender for the first time in about 3 weeks and the MMB doesn’t work for some reason. It won’t rotate around the object and it won’t pan when I press down SHIFT. Only thing that happens is the “Compiled with Python version 2.4” window comes up. I just installed a new GPU (NVIDIA 7600 GT) could that be the problem?
Pull the header at the top of the screen, and select the view and controlls button. Make sure that Emulate 3 Button Mouse is selected. There you can also select alternate view, zoom, and pan options.