I am an experienced LR 1, LR2 and LR3.5 user (currently using 3.5 on Mac OS 10.7). For some reason, however, I cannot import several folders of TIFF files that I have prepared for a project. When I click on each folder, all of the images appear as they should in the import module. Each one is checked. Yet, when I click on "Add" at the top, nothing happens. I am completely baffled. I have never had anything like this happen before. I tried to import several folders of TIFFs today and got the same result every time. Any sugestions?