From the images in the video, the blogging from last year and the fate of previous missions, it seems likely that a major factor in the shutdown was dust on the solar panels[1] which combined with low-light winter conditions to compromise the health of the electronics when they could no longer be heated. Future rovers may be able to self-clean the panels[1], giving a much longer theoretical lifespan (at least for this component).

[1] http://en.wikipedia.org/wiki/Cleaning_event

[2] http://www.technologyreview.com/printer_friendly_article.asp...