A slightly different subscription problem

I have a subscription for 3 computers that is good until July 2012.  It was loaded onto this computer in September 2011.  Now I have a big red X on the Norton icon and a window says “Activation Required.”  I don’t want to Activate again on this computer because there is another computer at my vacation house which really does need Activation and when I finally get there, I will Activate it, and I want to save the last Activation for another computer.  Thanks in advance to anyone who can help.