If you are running Mac OS X Snow Leopard, run Software update and claim your new upgrade, especially if you plan on ugrading to OS X Lion.
Apple Menu -> Software Update
As per Apple:
The Mac OS X 10.6.8 Supplemental Update is recommended for all users running Mac OS X Snow Leopard 10.6.8 and resolves issues with:
- Transferring personal data, settings, and compatible applications from a Mac running Mac OS X Snow Leopard to a new Mac running Mac OS X Lion
- Certain network printers that pause print jobs immediately and fail to complete
- System audio that stops working when using HDMI or optical audio out
For detailed information on this update, please visit this website:http://support.apple.com/kb/HT4561.