Welcome to the forum,
Q. Is the license file saved without modifying it? A in a place without accessibility problem?

Q. Did you tried to reboot the machine?

Q. I not understand one thing: you have installed the new version over the old one that wasn’t working?
1)If the answer is yes try to uninstall the console
2)Control if exist this folder C:\Documents and Settings\All Users\Dati applicazioni\AVAST Software\Administration Console (control if you’ve the rights to access here), if yes delete it
3)Try to install again, but insert the license during the installation.
4)If the problem still try to request a new license file by contacting your reseller, or try to go here
http://www.avast.com/resend-license-paid.php