Given that the iPhone is all but undocumented at the moment with the SDK not promised until February, I find that it often helps to add the following code to my classes. It allows me to see what methods are being invoked and create those as needed.

// Peekaboo. Uncomment to reveal selectors during runtime

-(BOOL) respondsToSelector:(SEL)aSelector {

   printf("SELECTOR: %s\n", 

      [NSStringFromSelector(aSelector) UTF8String]);

   return [super respondsToSelector:aSelector];

}