Limit upgrade version ?

I bought one year ago (march 2009) a licence for our personnal DJ in our non-profit home for mentally disabled people.
He played with the laptop for 1 year so i ask him to give it back to me for cleaning, updating OS (Ubuntu Studio) and updating UltraMixer.
I installed V2.4.0 but UM says my licence key is not applicable to this version. Grrr ! (Quite short for only one year upgrading).
So which is the latest version number i can use with it ?
I found 2.3.8, but before trying, is it ok ? Or is there a 2.3.9 version somewhere i could use ?
Thanks a lot,
PS : Licence name and buyer is Director’s name : Michel Laurent.

You are able to update to UltraMixer 2.4 for free.

Please activate UltraMixer with your personal licence key. Here you can find a step-by-step tutorial: