Microsoft must be rubbing its hands with glee. Mac users are reporting a major problem with Apple’s new operating system, Mac OS X 10.3, better known as Panther: it erases data on external drives. For many this is fatal, Wired reports, since many Mac users backed up their files to an external FireWire drive before installing the Panther upgrade. In some cases, the glitch erased files on the main machine and the external backup.Apple says it is working on a fix.