Quote Originally Posted by AutumnBreez
Also, it may be that your seat is too high that your having to reach and pointing toe down more then heel down during your down strokes. Possible that your saddle is cutting your circulation off somewhere down the back of thighs. It's crazy isn't it...the numerous factors for each persons individual issues.
If your saddle is too high it would cause pain in your knee before your foot went numb. I have clipless and find that when riding in higher temperatures my feet swell causing my foot to go numb. Going to a lighter weight sock and being able to loosen the velcro straps on my shoes during a ride made a big difference for me.

Along those same lines - are your shoes the correct size?? What about changing the liner in your shoes?

If all else fails you may consider having a professional bike fitting session. I know that some riders need to have shims placed in their cleats but all of the 'experts' that I have talked with say that that is something that should be done only after having your bike fitted by someone who really knows how to fit a bike.