iPhone backup or sync issue "unknown error occurred (-50)" I recently switched from iCloud backup to backing up to my computer since the iOS 8 update seems to have doubled the size of my backup and it no longer fits on iCloud. 

When backing up to my computer by pushing "Back Up Now" in iTunes, I get an error message:


  The iPhone 'X' cannot be synced. An unknown error occurred (-50)


The last backup time does change, and it isn't saying that the backup failed, but it is odd that I get that error every time.

I am telling it to not backup any of the apps, because I don't want all that dead space on my laptop. The error seems to happen after the backup and when the sync process changes to "Transferring purchases from X"

I searched around and wasn't able to find a satisfying definition of error -50 does anyone know what it is?
I got this error just now. My Mac mini was connected to my LAN via WiFi and also via Ethernet. That was working ok, but I was trying to get the phone to sync via Wifi (still can't get that working). 

Anyway, I pulled out the Ethernet cable. Plugged the phone in via USB and when I clicked Sync I got the (-50) error you describe.

My solution was to exit iTunes, and then launch it again. This was enough to get the phone syncing with no error.