That's strange...
Yes, PBR does use IOS21.
But it's such an old game... it shouldn't have any problems.
Is it the same region and video mode as your Wii?
Is it a retail copy or a backup copy?
What "syptoms" ocur when you try to run it? Blackscreen?
Do what DeadlyFoez stated and run it through Gecko OS, and tell us what happens.