When I started my day I noticed that my Desktop Time Machine icon was missing. The TM preferences panel indicated that it had been "disconnected", and it hadn't backed up anything for ca 8 hours.

Checking the Console log I was informed that the standard backup had failed due to
"Error -35 while resolving alias to backup target" and subsequently
"Backup failed with error: 19".
I have no idea what those errors are or might indicate ... and would like to know.

I ran Disk Utility (Repair Disk) on the backup hard drive (Western Digital My Passport 0740 1TB USB Drive) which found the media to be OK but when I ran Repair Disk on the volume it supposedly "stalled out" with over an hour left to run. When I cancelled the repair, it seemed to be happy and even ran a backup (ostensibly) successfully.

Nothing else seems to be awry with the iMac (2.5GHz Intel Corei5 / 4GB 1333MHz DDR3) running Mac OS X Lion (10.7.5).

Any explanatory commentary out there?