CS6 serial number now invalid?

I bought CS6 student and teacher edition a while ago. I had all sorts of problems with the initialization. I installed one version on my macbook pro and one version on my macbook air as I work from home on one and travel with the other. About 1 month ago my illustrator, in design and photoshop ceased to open. I get an error message saying that my serial number is invalid, and already used on a maximum of two machines, that I need a new serial number. I have only ever had the program installed on two machines. I tried to install it on my old macbook pro but it was too old to take the newer version of the software so I couldn't even install it, let alone activate it. (The new macbook pro was a replacement).

I have no idea what to do. Other than uninstall and reinstall all the programs which is a complete pain.

With all the issues I had just getting the software this is the last thing I need