Yeah, the protein causes either too much or too little acidity in her stomach, cant remember which. Seafood is strictly off the menu because of this, which we both hate, 'cos she loves tuna and I love giving her things she loves :p
According to my vet, my kitty probably got oxalate crystals from too much protein combined with too little exercise. I always gave her a high power protein diet, either the best brands or raw, but since I live in a small apartment, she doesnt get to lead the wild life that such a diet is...