My Macbook Air’s Software Update insisted on trying to download the SMC 1.2 firmware update everytime since it came out. Running the update utility just caused a strange dialog box to appear: “damaged or incomplete.”
Very annoying. I don’t know what made me run the binary from the terminal (shell) command, but that did the trick. The expected message showed up, machine rebooted, updated the SMC firmware to 1.2 and all is well again in Software Update land.