I've been trying to catch Raikou on Soul Silver for ages now. I caught Entei with my second pokeball so I have no idea how I'm having so much trouble with this one.
It's down to 1 hp and it's paralyzed, and each time I send out Snorlax and use block. Then it uses roar like one move later and disappears. I've tried using block, then switching to Sneasel and using taunt, but then it just flees again.