Subscription/reactivation

I have NIS 2011 on 3 computers with 318 days left on the subscription.  This morning, 1 computer says there are 0 days left (the other 2 still have 318 days left) and says I need to activate.  I tried but then there is an error message that I have exceed the the allowable number of installations.

I have uninstalled, and reinstalled NIS 2011 but cannot activate because of the exceeded message.

I had an automatic subscription renewal on 4/27/11 and everything was fine until today.

What do I do now?