I don't know if this is a good answer for everyone, but it worked for me. Mine began to hang immediately upon clicking on "Import" or file / import photos. No particular reason that I know of. Lightroom does that type of temperamental thing periodically. I was not getting an error message, just the spinning cursor and "Not responding." Previously, I would lose 2-6 hours going through these forum discussions, gradually finding some way to de-bug the program. Today, I didn't have time for that nonsense. After losing about an hour to the problem, I developed a work-around. I created a folder on my desktop and labeled it "LR Import." Leaving the folder empty for now, I went to file / auto import / auto import settings. I told Lightroom to auto import photos contained in the "LR Import" folder. I applied the new auto-import rule. Then, I put the photos that I wanted to edit into my new "LR Import" folder. Lightroom promptly imported everything in the folder. I was able to keep working. I'll go back and de-bug the import button problem someday when it is less inconvenient.