Thanks for the reply, Arpit. I'm keeping your note handy, but won't try it right now. I finally "solved" this mess for the moment though by no means fixed it.
Much experimenting showed that Photoshop CC (last version) and Lightroom 5.5 (new version) play well together. So I rolled back my Win 7 system to before I installed PS 2014, removing it.
Now I can work again, though without the new version of PS.
As far as I'm concerned, it's up to Adobe now to fix this mess. One commenter on another thread - Adobe staff, I think - said they were busy with other fixes and this wasn't a priority. I hope s/he is wrong.
Thanks for all your help.
Ed
http://feedback.photoshop.com/photoshop_family/topics/photoshop_cc_2014_wont_load_files_in to_photoshop_layers_from_adobe_bridge_cc/replies/14456669