update for avast! home edition 4.8 fails

[abcstu]

... with message "The license key for this product is temporarily disabled
--your system time/date has changed; fix it and enter the license key again."

But the system time/date was untouched.  I updated the time date from Microsoft's ntp server and tried re-pasting license key into dialog.  Still the problem.  I then got a new key and tried that.  Same story.
I'd really like to use this, but, if it cannot update, I must find another solution.  Yours looks very good, with many good ideas, but this update lockout is a problem.
I have changed nothing about firewall since installing avast!.  I have installed spybot 1.6, but noticed no trouble with it.
Any help appreciated.

[Lisandro]

Did you use the trial version period? How long did you stay using it? Reinstall it?
I suggest an installation from the scratch:

1. Uninstall avast from Control Panel first.
2. Boot.
3. Download the latest version of Avast Uninstall and use it for complete uninstallation.
4. Boot.
5. Install again the latest avast! version.
6. Boot.
7. Check and post the results.