Click on the little box on the left side of the update and select do not show. you can add it back in latter if you need to. Also you can set update to just notify when updates are ready and you can install them when you want to.
Thank you almartin. That will certainly cause it not to appear in the list. However it still leaves me not knowing why it happens on one machine (the laptop) and not the other. Can you shed any light on that?