Bill's story. I've had this problem when I was still in school, and I went to the doctor. Oddly, it turned out that it was my SHOES.... or more precisely, the way my shoe fit the build of my right foot in particular in combination with the way I laced it!
I agree that you should have the doctor check it out. It could be something very different than what I've experienced, which was nerve-related, apparently due to the pressure.
I'll also add that I wear a size 13W (or EEEE) running shoe, and I've had to get more in tune to the different fit of different manufacturers and styles, because there's a wide variance when you get into "oversize" and "overwidth". But I can also share that since I (because after a number of tests that would just boggle your mind) figured out the shoe thing, I also figured out it happens on multiple shoes that fit well, seems to involve the amount and distribution of the pressure of the lacing/tongue around the top of my foot and seems to impact either the veins or nerves there on the top of my foot or both.
I tend to run long distances for "joggers" and medium distances for "runners". It usually happens now very rarely, probably because I'm hyper conscious about my lacing (not TOO tight, not loose, EVENLY DISTRIBUTED all up the lace area, and not knotted too tight at the top). And now when it does, USUALLY a redo of my lacing and a short walk to get my foot feeling comfortable again, then I'm back for another 5 or 10 miles without problem.
Good luck - running is AWESOME, and when you can't and want to or when it gives you pain, it really blows. I'm just getting back into it and working up to long runs again, but I'm addicted already again.