Concentrate on why Photoshop can't save. Lightroom has nothing to do with this - it's just a background script that keeps track of the file and adds the location to the Lr catalog.
You never save "to" Lightroom. Photoshop just saves to a location on disk just like it always does, with or without Lightroom running.
If the Photoshop save never completes, maybe it's a permissions problem on that folder.