I though the body couldn't use anything more than 200 grams in a day? 500 grams damn
Depends on the person, and if the body is anabolic or not. If not you beating your head against the wall and putting you kidneys in the "Crippler Crossface". - Sorry Chris Benoit..rip.
On a side note I throw carbs in with my shakes, mix it with Fruit Punch to get some quick that will burn off fast, and usually use carbs like brown rice and sweet potatoes with my solid meals.
Just gotta find out what works best for you. If I go low or no carbs, I actually lose weight.
Edit: When trying to increase your protein do it in a gradual progression, it is hard to do. Just like dieting down, most quit before they hit their goal. Aim for 1g per pound, then 1.25g per pound etc.... this will make it comfortable and get your body used to bigger portion sizes.
Once in the 400g/day range You may find yourself drinking protein shakes with meals too.