updated 08:55 pm EDT, Thu October 31, 2013
Earlier, later models not affected; Apple likely to resolve issue soon
Storage accessory company FirmTek has reported that a specific model of MacBook Pro has mysteriously lost support for its own ExpressCard slot under OS X Mavericks (10.9). Users upgrading a 17-inch model from 2010, otherwise known as "MacBookPro6,1" under the extended "About This Mac" information, will find that cards of any sort inserted into the built-in ExpressCard slot do not work, even after drivers are reapplied. The problem does not effect earlier or later models.
The problem only surfaces when 10.9 is running, making it a software-only issue that should be relatively easy for Apple to fix. The company is aware of the problem but has not issued a statement or timetable of when the problem will be resolved. FirmTek is advising 2010 17-inch MacBook Pro owners to hold off on upgrading until Apple has a chance to post a solution.
Those users who may be having problems with ExpressCard cards on the 2009 or 2011 17-inch MacBook Pros after installing Mavericks should re-download and re-apply the driver for the ExpressCard device, which should clear up any issues, the storage maker reports. The issue on the affected model also means that drives that connect through an ExpressCard USB, Firewire or eSATA converter card are no longer mounting.