Today I was working on Numerology for the iPad and I was trying to implement a date picker inside a popover. You can’t just put a UIDatePicker in the popover because you need a view controller. So I created a view controller and called it UIDatePickerViewController. It simply would not work. All I would get is a popover with a black area. I couldn’t figure out what was going on. Then I decided to just use the UIViewController class but load in the nib I created for my view controller. Viola it started to work. Then I realized my class name was the problem. I renamed the class DatePickerViewController and it worked as well. Somewhere Apple must have a private class called UIDatePickerViewController.
Bottom line: Don’t use class names similar to Apple’s class names. It will bite you sooner or later.
Apple quickly approved 
Numerology 1.8 and Numerology Lite 1.4 have just been submitted to the app store. The main new feature here is Facebook integration. The price is going to be raised to $4.99 so if you plan on buying Numerology, but it now and save a buck. More details once the app is approved.