Preview locks up during import of photos
I am trying to import photos from my camera (RAW format) the way I have done for years. Now my iMac locks up in the middle of importing the second photo almost every time. I need to cancel the import, cycle power on my camera and start again. If I'm lucky I get another one or two pictures before it locks up again. This is new since the most recent software update. Strange thing is that Preview does not show that it's "not responding". It just can't continue with the import. Suggestions please?
iMac, OS X Yosemite (10.10.4)