iphone photos sync failing 10.10.3
Since upgrade to Photos with MacOS 10.10.3 my iPhone (4) is failing to sync photos as iTunes (12.1.2.27) says the photo library is "not ready".
Worse still the pane to deselect syncing of photos never appears when selected (just a waiting wheel).
Does this mean the location of the Photos library is corrupted in iTunes?
How can I correct this if the pane to select the photos library never appears?
PS I tried restoring the phone but that did not help. Music will not sync either as the photos library problem terminates the sync before it gets to music.
iMac, OS X Yosemite (10.10.3)