"invalid serial number" error

Hi there,

I am trying to activate CS5 on a new laptop. I have the software already installed on an old laptop which has become my home computer -- I understand i am allowed to use the software on two personal computers but I get an error message "invalid serial number". Please can someone help me. I have called Adobe and they have confirmed that the number is valid but said I need to reach out to this community to figure out why... a little infuriating. I've been trying to solve this problem for 3 weeks !!