Update to the Sigma 50mm f/1.4 Art malfunction. I sent the lens to Sigma USA for repair. Fixing the lens cost $175 + $25 shipping + tax. So, for a little less than $220, my lens arrived repaired and in perfect working order. It even looks like they cleaned the lens while they had it. It was in incredibly good condition when I sent it to them, cosmetically speaking, but now it looks brand new.

Now I have a dilemma in regards to 50mm lenses -- which one do I keep? The Sigma 50mm Art or the Canon 50 f/1.2L? I wouldn't get as much for the former if I sold it and it's sharper than the Canon at comparable apertures, but the Canon has a wider aperture and is weather-sealed with a filter in place. Hmm...