If you are new on Dolphin, check the requeriments thread (general discussion). I have too much problems like you, but I got the Dolphin 3404 (through other link) and some problems disappear. I still running Brawl with 3FPS!
Ok, check the thread: http://forums.dolphin-emu.org/thread-4.html
Ok, check the thread: http://forums.dolphin-emu.org/thread-4.html