The MacRumors Forums, Western Digital's forums, and Apple's Support Communities all had threads about lost data after connecting Western Digital external hard drives to computers after updating to Mavericks.
The WD SmartWare update is available for download from Western Digital's website.WD is happy to announce the release of WD SmartWare Version 1.3.6 for Mac 10.5-10.9.
Fixed an issue related to reports of some customers, under certain conditions, experiencing data loss when updating to Apple's OS X Mavericks (10.9).
Article Link: Western Digital Releases New Hard Drive Software After Mavericks Data Loss