I was having the same issue, primarily after a refresh. Why it occurred, I have no idea. It can be fixed by temporarily moving the default location of your entire Pictures library. It doesn't matter which directory you change it to. Also, there is no need to move the files to that location (just keep them where they are); just the default folder need be moved, so when it prompts you, simply click "no." Then, after that is done, move it back to your default location, wherever that may be. You may or may not be having similar issues with your Skydrive account. If you are, move the "Photos" folder anywhere and then move it back to the default location on your Skydrive account. That should also fix the issue if you are experiencing it on Skydrive. Hope this helps.