Numb foot while running..what in the world????

A couple of things to think about:

Lacing of your shoes, Runner's World had a great article about lacing shoes to avoid numbness or ill fit.  Make sure your shoes are wide enough too.  I need a shoe with a wider toe box so that when my feet swell on longer distances I am not squeezing the nerves in my feet.  I have already had two neuroma's removed from my left foot as it is.

Have you been fitted for shoes?  Sometime the running shoe that seems ok for shorter runs does not work for the long run and you need to be fitted for your shoe at a running store.

Age of your shoes. If your shoes are old they may not have the cushion left to take on the pounding of longer runs.  I only put about 400 miles on mine, in part due to the fact that I stride heavy and need shoes with good cushion and inserts.

You need to provide more information to figure out what the problem could be.  As noted above, the shoes might be too old, or too tight, or laced oddly.  I recently got a new pair of shoes and when I set up my Yanks on them, I had the one too tight, which gave me a similar problem over the course of about a month's use.

So, details about the shoe, the lacing, the running conditions (too hard/soft surface?) and if you ever had similar problems before would be needed to give you useful answers.

I've had this problem before during a race. Never really was a problem training but my foot swelled during a race and the shoes were too tight and had more pressure on nerves which cause numbness.

Be really careful with yanks and other quick lace systems they can easily be laces too tight.