Never call dealloc except as [super dealloc] at the end of your class’s dealloc method. The release method relinquishes ownership of an object. When a Cocoa object no longer has any owners, it may be deallocated — in which case it will automatically be sent a dealloc message.
If you’re going to program Cocoa, you need to read the Memory Management Guidelines. It’s incredibly simple once you get over the initial hump, and if you don’t understand what’s in that document, you’ll have lots of subtle bugs.