There cuboid bone is notorious for causing sudden foot pain (especially with a pop) after running a lot on uneven ground. If the pain is on the outside -middle of your foot, then I am willing to bet that is what happened, possibly to both you and the OP. You can get an adjustment where a PT pops the bone back into place for you. As long as you didn't tear anything while it was popping out of place, you should be fine.
Here is a picture of the cuboid bone's location the foot.
http://www.aafp.org/afp/20040215/865_f1.gif
If that is where your pain is, you are in luck!
Here is some information on the symptoms, diagnosis and treatment of a subluxated cuboid bone:
http://www.myfootshop.com/detail.asp?Condition=Cuboid%20Syndrome
Hope this helps!