Blender Reading MMB as LMB/ Orbit Not Functioning

Hi guys,
I’m pretty new to Blender and I’ve encountered an issue. I have a Mac running Snow Leopard. When I press the MMB and drag, I can no longer orbit or dolly. Clicking the middle mouse button is instead treated as a left click. I confirmed this by going to the View3D Rotate settings. It was set to MMB. I clicked where it said MMB, and it prompted me to press a new button to set for rotate. I clicked the middle mouse button and read that as LMB. I tried with a totally different mouse and that has not worked. I have uninstalled and reinstalled Blender. What’s strangest is that Blender was working perfectly last week.