My original post at http://www.pizzamaking.com/forum/index.php/topic,29234.0.html
has gotten over 500 views (didn't expect near that many) so now that I believe I've found the answer I thought I'd post it in case anyone else has a similar problem. (By the way thanks to those who replied for the helpful suggestions.) My original problem was that my pizza had no crumb, was not fully cooked on top and was stiff as a board. After reading the recipe and remarks at this link http://www.pizzamaking.com/forum/index.php/topic,1707.0.html,
I realized that the first problem I had was that I was not ensuring that my yeast was properly activated. When I started out a year or so ago, I started with active dry yeast, but after a while I switched to instant yeast, and after some very good results with cold fermentation, I got a little complacent and began adding the yeast right to the (chilled) flour and added cold water, then mixed the dough and put it instantly in the fridge, thinking that slowing the rise even more would give an even better, more complex flavor. (Previously I would hydrate the yeast in warm water and proof the dough slightly warm oven for at least an hour before putting in the fridge.) After reading the recipe, I went back to my original method of hydrating the yeast and proofing at a warm temperature for at least an hour before chilling the dough. I only roughly followed the recipe. I didn't use any honey, I didn't use the exact percentage of sugar, salt, or oil, but I stayed within moderate range of the amounts given and the results was one of the best pizza's I've ever made. The flavor was exquisite. (Though I must admit, I still have a preference for the artisan flavor - flour, water, salt, and yeast with little or no sugar or oil.) I'm not surprised the flavor turned out so well because I noticed a definite improvement in the texture of the dough after proofing it last night. I did chill the dough for about 16 hours before making it, as I still believe in letting the dough build up the proper acids by sitting in the fridge for a while, and while it was chilling I realized another possible underlying cause to the problem with my dough. I wondered if maybe using chilled flour and cold water could have inhibited the formation of the gluten network. I had read a post from a bread baking website some time ago that stated that flour and water should always be at room temperature before using to make any type of bread or the results will be less than satisfactory, but for some reason I forgot this as I began to gain experience. After remembering this I realized the third (what probably should have been the first realization) and most obvious problem. When I started out I was using bread flour, but a few months ago I started using a mixture of half bread/half all purpose to save a little money. I think my dough paid the price for it. I also just noticed today that the top heating element in my oven doesn't turn on unless I use the "Broil" setting, but I believe this to have little relevance in the proper formation if the crumb because I've achieved great results prior to realizing this. For anyone looking for a good recipe though, try the one in the link above. You will not be disappointed.