Long ride problem

[VeloVT]

Hmmmm.... how much are you drinking? You say you're well hydrated, but this sounds in part like it **could** be dehydration... and low blood sugar.

Edit:
Also, have you been training at this level for a long time (over a year), or have you ramped up training pretty quickly? I've never read anything about this, but in my experience running at least, your body gets much better and more efficient at regulating glucose as you train, but it takes a while (several months) training at a consistently high intensity for this to happen. I really noticed this last year when I was training for a marathon, and I'd go for runs or rides with my boyfriend, who was in decent shape but not "training", and he'd get really low blood sugary (that is, not just sore, tired, etc but spacey and lightheaded) far before I would, and he also wasn't very good about realizing that it was happening, until I called his attention to it. For quite a while I had to remind him every so often to have some calories, so we could prevent any catastrophies (he actually had a crash that was basically due to inattention/spaciness due to low blood sugar, so I became maybe a little hyper-vigilant about it). But the thing was, being less well trained at that point, he was BOTH not able to go as far on the same amount of fuel AND not as aware of the fluctuations of his blood sugar/energy level as I was, being relatively well trained at that point (though not now, unfortunately!).

I don't know if this applies for you in any way, but I thought I'd share just in case...