I could be wrong, but I suspect that Nintendo (probably) had a pretty big game that was supposed to be released for the holiday season that was delayed. I would imagine that this delay would be justified because of a combination of factors including the Wii having the strongest third party line-up in a holiday season Nintendo has seen in a very long time, Nintendo's software sales tracking (far) above where they projected them being, and the game needing some work to meet its potential.
If I am correct the interesting thing is how much more annoyed Nintendo fans were by an unannounced game being delayed than they have been from announced games being delayed several times; because the game wasn't announced, people assumed that Nintendo wasn't focusing on them anymore rather than Nintendo trying to provide the best game experience.
