Cannot edit photos

I’ve tried this on a few sites and it works fine, but one of the sites I have, I cannot edit individual images. When I click on edit, the screen goes dark like something may happen, but it just hangs there. So all I can do is click the screen again and it goes back to the list of images. And I can only use images that have been imported from NextGen, I can create a new gallery, but then can’t add any images to it. It does the same thing. Are there any known plugin conflicts that you know of? I even changed my theme, as I thought that could be an issue, but it is the same.

Thanks