Runner's Forum: Hitting the Wall (how not to?)

Soon, I will start training for my 3rd marathon.   Twice now, I have "hit the wall" at mile 22 which prevented me from reaching my goal time.   I trained well per Hal Higdon's guide and ate properly (even went to Sports Nutritionist last year).    I used GU in Year 1 and eGel last year (per the directions).   I read that one should consume 300 calories per hour during the race, of which 90% is Complex Carbs.   Seems that a product called Carbo Pro just might be the magic formula.   Anyone have pearls of wisdom here?  

Quite a few people feel like HH runs a little short on mileage, especially on the novice plans. Hal himself suggests increasing the mileage if you feel the program is not serviing your specific needs.

Another issue may be pacing. If your not leaving anything in the bank you're more likely to bonk. How are you setting your goals? Better yet, what are your goals, and how do they correspond to your training plan?

Posters, thanks for some great comments.   I will "graduate" to Hal Higdon Intermediate 2 plan which includes two 20-mile training runs.  HH is very clear that these long runs of 17,18,19,20 should be done 30 - 90 seconds slower than race pace.   For me, that's 9:00/mile.  For both marathons, I kept this steady pace and then hit the wall hard at mile 22.   I think another 20 miler will help this year.  Now I'm off to listen to the podcast suggested above.  Thanks again.