Transient disk backup failures on full and incremental backups with the mysterious 64 reason code.
Messages like
BackupDiskFile::RequestDurableMedia: failure on backup device '<\\jewel\sqlbkup\devldbs5$i1\ACCPAICN\ACCPAICN_tlog_200304140802.TRN>'. Operating system error 64(The specified network name is no longer available.).
BackupMedium::ReportIoError: write failure on backup device '<\\jewel\sqlbkup\devldbs5$i1\ACCPBHIS\ACCPBHIS_tlog_200304140803.TRN>'. Operating system error 64(The specified network name is no longer available.).