My Wii is at 3.2U with a WiiKey 2 v1.2 firmware and I have a similar problem with "sonic and the Black Knight" and "Need for Speed, Undercover" I read that these two require an update to 3.3 or 3.4 but there's no way I'll do this as all my other backups run flawlessly! In your case, there are probably patches to run through HomeBrew, but why bother if your other backups run?? Just my $.02.
I found another two backups that won't run: Broken Sword, Shadow of the Templars and MLB 09'. I chose the WiiKey 2 because it could play backups from any region and it's worked fine until some of the recent releases. I'm hoping a firmware update will solve this (if that ever happens)!