I just imported some photos from my iphone ... they were ... already on my Mac anyway.
I like you already.
No one answered for 15 hours, so I'll take a shot... and bump your question to the top of the queue, and maybe you'll get some answers. I'm willing to take the risk of losing some points to do that for you. That's the kind of guy I am :)
The thing about data is that sometimes it gets corrupt. I don't think that's what's happening here, I'm just saying that sometimes data gets corrupt, whether its cosmic rays or eddies in the space-time continuum. There's nothing you can do about it other than have backups. And in this case, iCloud backed up the photo you can't edit in at least 2 places, if not more. So why bother with this photo you can't edit and save, when you just said that you had another copy of it?
That being said, usually the reason you get a message like that means that the file is open somewhere else.
Try quitting and relaunching the application. ;-)
If that doesn't work, try rebooting.
If possible, import the duplicate photo that was already synced from iCloud on your Mac into iPhoto, and see if you can now edit and save the photo.
If that doesn't work, try identifying the location of the photo file in question. Once you have the path to its containing folder, open Terminal, type cd and a space, and drop the folder in the terminal, and hit return. Then type:
and look for an invisible lock file with a file name that begins with a period. If you discover one, delete it with this command:
then check and see if you can open, edit and save the photo in question.
also iphoto won't allow me to reveal the file, the reveal options are greyed out
Does iPhoto tell you the file name of the photo when you hover over it, select it, or select it and click the info button in the toolbar? Perhaps using the filename you can search for it directly with Spotlight in the Finder.
Do you see an exclamation (!) mark?
iPhoto Library Manager