Apple has released
ExpressCard Update 1.0 for MacBook Pro laptops. The update requires Mac OS X v10.4.7 to install.
According to Apple, the update “resolves an issue that prevented the system from sleeping when some cards are inserted in the ExpressCard/34 slot.”
ExpressCard/34 is the newer, smaller expansion port that replaced the PC Card slot found on PowerBook G4 systems. It improves data transfer speed and sports other enhancements not found on PC Card slots.