When I first went 100% raw (last summer), I had SO much gas that it was almost ridiculous. No, wait...it actually was ridiculous! Not 2 minutes would go by between gassy...um...outbursts. Now, none ever, unless I eat nuts. Foods that supposedly cause gas (onions and broccoli) have no effect on me at all. I think (but am no expert on gas...lol) that yours was caused by exactly what you think - the raw vegetables. They act up with cooked foods and toxins in your bowels. Whenever my husband (who is not raw) goes out for a raw meal with me, he complains bitterly of gas for the next two days, while I go blissfully about my day, gas-free :)
Gas is definitely a transition-to-raw by-product, just as you suspected it might be.