Mis behaving Tab

The tab key misbehaves when you modify a value (in my case, a string value with standard editor). It works fine if you don't modify anything: Tab moves to the next property and Shift+Tab move to the previous. But when you modify a value and press the tab key it --- will I don't know where it goes but not to the next property. If you press the tab key again, it goes to the category. Not a happy place if your property was way down the list. This only happens with categories. A property list without a category -- the tab key works fine even when modifying.