first, check your monitor refresh rate, it might have somehow gotten chnaged to 60hz.
second, check the "video" setting in AH, it may also have been changed from unlimited to a capped "60fps"
your resolution 1280 may be the culprit here, as not all monitors support higher resolutions at a higher refresh setting.
these are the most likely factors, especially since you're seeing a steady 60fps; the implication is there's something capping your refresh.