I want to deactivate photoshop cs5 on my macbook, but under help, the "deactivate" word is dimmed,

I just install and activate photoshop cs5 to my macbook from my Imac computer to do some photomerge work, as I am having trouble in doing the photomerge on Imac (the computer Imac goes through the process, but will not hold and deliver the merged image, just every time after all the process steps, it goes back to the original images) Now I want to reactivate CS5 on Imac, I understand that I need to deactivate the Macbook version first, but now the word DEACTIVAT under help is dimmed; . I double check with My Imac version, The word  DEACTIVATE is dimmed too, and keep on to have the diaalogue box appear and saying that activation limit is reached.

So now the situation is that I can not used photoshop CS5, on either of them ,( Imac and Macbook,) the word  DEACTIVATE is dimmed on both computers, so what should I do? THE SERIAL NO IS xxxx-xxxx-xxxx-xxxx.

THANK YOU

CATHERINE