Ok, the world is coming to a crashing halt --- my camera will not download the photos!!!!

It used to be that when I plugged in the USB, a window would pop up asking me what I wanted to do with the photos. I'd select "Save to my computer", and be on my merry way. Tonight, insytead of that pop-up I got "Removable Disc (G" And it won;t let me do ANYTHING.

Ok you computer gurus out here, what's wrong? What happened? And most importantly, how do I fix it?