Lack of Shift
I just picked up an Eclipse Carbon 7 bicycle with an Ultegra 600 group. The bike has not been ridden in years, so before taking out onto the road, I threw it on my trainer in order to sort out the fit and rideability. As soon as I downshifted the rear cassette into the highest gear, I was unable to make the rear derail. do anything. I move the lever and the cable doesn't move, so I'm assuming that the cable is at fault, but it's still under high-tension, so I really can't imagine it being broken. The bike was stored in a basement, and while it was a damp environment, there isn't any rust on the parts or cables.
Push the mech with your hands, see if it moves. Maybe a problem with the shifter, mech or cable.
Most likely your shift cable is corroded inside the housing. If that's the case, I wouldn't bet on the brake cables functioning right either. Fortunately, the repair isn't a big deal.