In Mac OSX 10.6.4, I'm trying to change the default application for opening .cc files from Xcode to MacVim, but Xcode or OSX won't abide. Here's a screenshot:

Notice how the clicking "Change All..." to MacVim results in the dialogue asking me to confirm the switch to Xcode - it's really hogging those files!
Why is this / is there any other way to change this?
Cheers!