Protein in race/training nutrition?

I'm trying to work out whether and how much protein I shoud include in my training/race nutrition for longer distances. So far I have only raced up to Oly distance, but I would like to step up to HIM distance next season. Last season, I used pretty much straight carb nutrition sources (gels & sports drinks w/o protein). This year, I tried Accelerade, both their gels & drinks, with 4:1 carb:protein ratio. It works okay for me on longer bike rides where I am going at a lower intensity, but I have found that when I'm pushing harder, and for long runs (even at LSD pace) they tend to cause some stomach/intestinal cramping. I'm not sure if it's the protein, or something else in Accelearde that causes the cramping. I tried a more dilute solution by mixing fruit punch flavored Accelerade w/ fruit punch flavored Gatorade, and still had the same issues.

So, I guess my question is three-fold: How important is protein in sports nutrition, especially for longer distances (like Marathon or HIM), any good information out there on what the optimal carb:protein ratio is (though I suspect it may vary from person to person), and if I *SHOULD* be including protein in my nutrition, what else is out there that I should try out as I prepare for next season? I realize it will take some trial & error to figure out what works best for me, but any recommendations would be appreciated!