What version of PCSXBox are you using? Also, you may want to reference this thread for information about specific games:
PCSXBox Compatibility ListIt looks like what you are experiencing is the same issue described in the compatibility list, so there isn't likely anything you can do about it. Though there is a chance that if you are using an older version that the newer version might improve things a little. Also, try disabling CDDA in the configuration options (hit 'X' when starting the game to see the options). This will disable the background music, but it often also results in a game speed increase.
PCSXBox is the only PS1 emulator the XBox has.
