Lightroom :: Image Edited In Photoshop Doesn't Show Up Properly

I have my photos on a separate volume at /Volume/Users/Lightroom Photos/…
 
Everything works fine except when I choose "Edit in Photoshop CS6", work on the image in Photoshop then save it. It gets saved back to the same folder as the original file, but when I tab back to Lightroom it just shows a square tile with a question mark instead of the new file. Tapping on the exclamation mark reveals that Lightroom thinks the new file is supposed to be in /Users/Lightroom Photos/…
 
For example the dialog box might say:
 
“_DSC3047-Edit.tif” could not be used because the original file could not be found. Would you like to locate it?
Previous location: /Users/Lightroom Photos/2012/2012-12-08/_DSC3047-Edit.tif
 
When in reality the original and the edit are both in /Volumes/Users/Lightroom Photos/2012/2012-12-08/ and there is not, and never was a /Users/Lightroom Photos/…
 
That is, something about saving back from Photoshop stripped off the "/Volumes/" from the beginning of the path. I can choose Locate and find it right where it should be and it will show up. Once it shows up the image tile shows the image but has an exclamation mark; tapping on that brings up a dialog box that says:
 
The metadata for this photo has been changed by both Lightroom and another application. Should Lightroom import settings from disk or overwrite disk settings with those from the catalog?
 
This is on a Mac and so /Users does exist but that maps to /Volumes/Macintosh HD/Users. I wonder if either LR or PS is confused by there being a /Users and a /Volumes/Users.
 
Editing in a Nik Plugin (e.g. Silver Efx) works properly, FWIW.
 
I am using LR4.2 and PS CS6 13.0.1 on OS X 10.8.2.