Lightroom no longer importing photos from Canon camera

I've been using Lightroom on my MacMini for ages and the import is really easy and always works - click import from Canon 6D and hey presto they're there. But not today. I think it may have been updated recently, which could have caused an issue, but not sure. Now when I try to import the images I can still click on the camera (so it knows it's plugged in), but it says:

"No images that can be imported were found in the selected source"

Nothing has been changed with the settings on the camera, so what's happening?

I'm on Lightroom version 3.1

Any help gratefully received!