Been going through a similar problem - takes 2-3 hours to show up usually. It's worse when I really crank hard or climb. Got the Specialized footbeds and I think they help quite a bit (my old insoles were toast), but did not totally resolve the problem. Lately when I feel it coming on, I pull up on my feet, either with the pedals fixed or while spinning; I can really feel the blood flowing back or nerves decompressing -- similar to standing after you've been in the saddle for a while. Still looking for a better solution...