Sudden, severe foot pain with some numbness.

Hi there,
Occasionally, I get a very severe pain on the bottom of my right foot. The pain seems to be on the inside of the foot (the side closer to my left foot). When the pain comes on, it is incredibly sudden, and does not seem to be caused by anything that I am doing. It goes away within 30 seconds or so, but during that time, I am close to paralyzed by the pain. My toes and that side of my foot also feels literally numb. I would say it happens once every two months or so, sometimes more frequently, but it is always a surprise when it does happen. Otherwise, I don't really experience any pain in either of my feet. I am not overweight and I do exercise moderately (elliptical 2-3 times per week for 15-30 minutes) but I have not seen any information anywhere that could possibly explain this pain.

If anyone could give me ANY insight, it would be GREATLY appreciated. My email address is hindymunt@yahoo.com. Thanks.