License is exhausted

My Problem is that my license is exhausted although it is available until 2013.
Knows anybody why this could happen ?? I m really helpless ???

is your computer time / day / month / year correct ?
if not adjust and reboot

Have you tried avast repair and reboot ?

For a repair of avast. Windows, Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.

Please, upload (attach) the avast log:
C:\ProgramData\AVAST Software\Avast\log\Setup.log
or C:\Program Files\Alwil Software\Avast5\Setup\setup.log

If the file is too big for the forum, post the last 400-500 lines of it.