Western Digital recently corrected a firmware issue in certain models of VelociRaptor where the drive would erroneously report an error to the host after 49 days of operation. Somewhat inconveniently for RAID arrays, if all drives powered on at the same time they would all report an error at the same time.
Informed speculation: the drive reports an error after exactly 49 days, 17 hours, 2 minutes, 47 seconds, and 294.999 milliseconds of operation. That is the moment where a millisecond timer overflows an unsigned 32 bit integer.