There is obviously something wrong with the expiry date "License is valid until: 12/31/69" because for a home edition it would be a max of 14 months and for a pro license it would be 12 months, so the expiry should be either 2005 or 2006.
Have you at any stage altered the system date that you are aware of?
I would suggest that you try a repair of avast. Add Remove programs, avast! Anti-Virus, Change/Remove button and scroll down to Repair, click next and follow. You need to be on-line to do this.
If no joy, uninstall reboot, install and enter the reg key again.