Why won't IPhoto import my pictures from cameras?

I've had my macbook air for about a year and a half and I've always imported photos from my cameras to it. Recently out of no where whenever I plug in my camera to import it works fine I select my images and once i hit import the blue bar at the top seems to go about halfway and just stop and the photos never import ill leave it there for a very long time then force quit because something is obviously not working right. Usually it takes a couple seconds do upload one photo now nothing happens for a while. This has been happening overtime i go to import from both cameras (I use a nikon dslr and a olympus digital camera) Also no error message ever comes up and I have a large amount of space on my computer so that is not the issue i believe.