Activation Error in Kaspersky 2012

I am trying to install Kaspersky Internet Security 2012 on my Windows 7 PC. But an error is appearing after I entered the product key of the software. I am using Kaspersky on my own PC only but I have installed it for few times now. I am really puzzled because I purchased this software few months ago only. Is it expired and do I need another activation key? Please send some help. Thank you.

Activation of Kaspersky Internet Security 2012
Activation error
Number of activations using this activation code has been exceeded
