Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble, Dave.
This could be an issue with the wii itself (compounded by the scratched disc), or a problem with the disc itself.
For the cost of a good cleaning machine, which may not help, it may be cheaper or more practical in the long term to just buy the game again, especially if you can get it used in good condition.
I'd start with a thorough cleaning of the console:
You can attempt to clean it by blowing out the disc tray/slot area with a can of compressed air for dusting computers (keep the can upright only so you don't get chemical propellant on the lens).
If this doesn't help, you can try a specialty cleaning disc (Allsop 23321 Ultra Pro Carbon-Edge DVD and CD-Drive Cleaner) which has little brushes that clean the lens more thoroughly.
Next, clean the disc further. The Skip Dr or Disc Dr products tend to be the best, ***** ***** can get a manual or motorized version: http://amzn.to/1PBCDTj
They can't repair deep scratches though, nothing can, so if you think it is anything more than very superficial, spend your money on a new game instead.