Apple has added a new article to the Knowledge Base regarding appearance of the buttons in some brushed-metal applications. Appleis Knowledge Base (sometimes referred to as the KBase) is a central location for all of Appleis support documents and other important information.
Users updating to OS X 10.2.3 may notice a change in the look of the close, minimize and maximize buttons in some brushed-metal applications, such as iSync, iCal, iChat, and Address Book. This is an intentional change. From Apple:
The close, minimize, and maximize buttons in certain applicationsi windows have a new appearance. They appear countersunk (rather than raised) and thus lack drop shadows.
- Address Book
It is possible this may appear in brushed-metal-themed applications that do not appear in this list.
This is deliberate design change. Not all brushed-metal-themed applications will automatically inherit this change (such as iTunes). No troubleshooting is necessary.
You can find the new Knowledge Base article at Appleis Web site.