Activate a second computer with my Adobe ID denied. Solution?

I bought a new computer and try to activate it with my ID. It would be the third devide : 2 computers, 1 eReader. Here is the message I get trying to sctivate this devide (free translation from french) : "You can get authorization for that computer only if  you do not use an Adobe ID allocated to another computer or mobile device. Please try again."

French version : "Vous pouvez accorder une autorisation à cet ordinateur à condition de ne pas utiliser un ID Adobe alloué à un autre ordinateur ou périférique mobile. Veuillez réessayer."

Any solution? I can't transfer borrowed eBooks from this computer (the only one I have now, as i'm travelling) to my eReader.

Thanks for help!