Just figured out what’s wrong. I don’t think there are any problems with the plugin at all. It’s the Magic-fields Plugin that’s creating the problems.
Edit:
For those who are using WordPress 3.0.1/ CMS Pages Tree View 0.7.4 / Magic Fields 1.4.5 Combination:
If you are having the same problems I had, just go to Magic Fields Settings and uncheck the checbox Hide non-standart content in Post Panel and that fixes the problem.
Cheers.