I've always been an "easy bonker," too, and I agree with the previous poster--you have to find a routine that works for you. On the bike, I don't have too much trouble. I just make sure I'm getting some kind of carb replacment (usually in the form of gatroade and an energy bar) every 45 minutes or so. On a run, I take in five good swallows of gatorade at least every half hour.
Here is the part that finally seemed to make a difference with me, though: the recovery. The way I understand it, if you replace your carbs within 10 min-1/2 half after hard exercise, your muscles take up more than they stored before--in effect training your body to store carbs more efficiently. Maybe someone who knows more about it than I can explain the science.
Anyway, once I started getting religious about replacing the carbs right away, I quit bonking almost completely. The only time I'm prone to it now is if I run before I've had anything much to eat for breakfast. Since the hot weather is here, I wanted to get outside before the temperatures got out of sight, so I thought I had to run before breakfast. Turns out, this is a mistake for me. I found out through experiemnting, though, that I don't have to wait two hours after eating before running (as I thought). Now I have a light breakfast and run 1/2-1 hour later and do fine. And as I said, if the run is going to be over 30 minutes, I take along gatorade and drink it during the run, before I start to bonk.
I almost forgot: do pay attention to what kind of carbs you eat and when. Hi GI carbs during exercise and immediatley after. After that, you'll want to do low to moderate GI--stuff that takes longer to digest so that the energy is released more slowly. That's what I understand about it, anyway, and it has worked well for me.
Also, one more thing: the post-workout replacement carbs will be utilized by your system faster if you have them in a 4:1 mix with a little protein. Good for muscle recovery, too.
You probably know all this, but I'm passing it along becuase it is what has finally worked for me. FWIW.