Updated Avast, now I get a "Unauthorized Windows Change" error

[ConjureLass]

I'm almost 100% certain that this is a problem with Avast.  I never had this issue before I updated it a week ago.  Now, sometimes when I start the computer it gives me the "An unauthorized change was made to your license" error.  If I reboot, the problem goes away and the system starts normally.  I also get the popup window when I simply leave the computer on doing absolutely NOTHING.  What's going on?  Is anyone else having this issue?  The computer doesn't do it all the time.  But I don't want it to get any worse!

Any help would be appreciated. 

[Lisandro]

Which is your Windows version?
Did you try uninstall, boot, install avast again, boot?

[ConjureLass]

I run windows Vista.  And I haven't uninstalled it yet, but I was thinking about trying that next.  Is there any way to find out what it might be interfering with?  Some sort of scan I can do?

[Lisandro]

Hmmm... I don't think it has anything to do with infection.
Which was your antivirus before avast?

[Nesivos]

I'm almost 100% certain that this is a problem with Avast.  I never had this issue before I updated it a week ago.  Now, sometimes when I start the computer it gives me the "An unauthorized change was made to your license" error.  If I reboot, the problem goes away and the system starts normally.  I also get the popup window when I simply leave the computer on doing absolutely NOTHING.  What's going on?  Is anyone else having this issue?  The computer doesn't do it all the time.  But I don't want it to get any worse!

Any help would be appreciated. 

You didn't say but do you know based upon the error message whether it refers to Avast or Windows?

[Lisandro]

Well... In my answers I always suppose you're referring to Windows... Am I wrong?

[ConjureLass]

It's definitely a windows error, not avast.  My suspicion that it stems from avast is mostly based on the fact that it never, ever did this before I updated the program last week.

Before I had avast I had norton, which was just so awful I deleted it and never looked back.  Is it possible there is some lingering files that are messing with avast?

[Lisandro]

Is it possible there is some lingering files that are messing with avast?

The Norton Removal Tool uninstalls all Norton 2003-2010 products from your computer.

1) (If possible) Remove Symantec products through Add/Remove programs from Control Panel. Boot.
2) Use Norton Removal Tool for Windows 2000/XP/Vista/7 or Norton Removal Tool for Windows 98/Me. Boot.
3) Install avast! (or repair the installation) and boot.

Norton is very difficult to get rid of

[safacto]

Just wanted to say I had the same problem on Vista x64. The latest Avast update seemed to change some security file in windows, giving me the "unauthorized change to windows" message which prompts you to re-validate windows. Unfortunately the windows validation website is broken and just continually redirects to a bing search page. No other windows functions except default web browser are available until after validation.

In safe mode I tried rolling back to an earlier restore point, and this initially worked, but after restarting a second time, the error comes back. Seems that Avast might be re-updating itself or something?

Uninstalling Avast got rid of the error. Think I might wait till the next Avast update before I try installing again...

Did full system scan (8 hours!!) with Microsoft Security Essentials afterwards and no malware or anything found.

Cheers,
Richard.

P.S. Had Avast installed for over a year before this with no probs, but this latest update just borked it.

[Lisandro]

safacto, I suggest an installation from scratch:

1. Download the latest version of avast! Uninstall Utility and save it.
2. Download the latest avast! version and save it.
3. Uninstall avast from Control Panel (if possible). If, for any reason, you can't run it, try booting in Safe Mode and doing it from there. Anyway, boot after that.
4. Run the avast! Uninstall Utility saved on 1. If, for any reason, you can't run it, try booting in Safe Mode and doing it from there. Anyway, boot after you've run it.
5. Install avast! using the setup saved on 2. Boot.
6. Register your free copy or add the license key for Pro. Or even upgrade your key from old versions.
7. Check and post the results. If, for any reason, you did not solve, try doing the step 3 in Safe Mode anyway.

[Hermite15]

use Windows Activation Technology KB file to repair the activation process
http://support.microsoft.com/kb/971033

(that's W7 version, google for Vista)

[Hermite15]

safacto, I suggest an installation from scratch:

... that's already what he said he would do (he has uninstalled Avast for now)

[cstro]

Had the same problem. Did a restore to a previous restore point so the Avast program was set back to 5.1 and I have stayed with that until a newer version of 6.0 comes out.

I have used Avast free from day one on this computer for more than 2 years, first time the update has caused this problem.

Windows Vista Home Premium 64bit.

[nokomis]

I'm getting this same thing. I never had Norton, only the free version of Avast. In the past week,whenever I boot up my PC, right after the Vista welcome screen, the screen goes dark showing a box that says "An unauthorized change has been made to Windows" and I can't access my desktop or any files. Restarting my PC will stop it, but it keeps recurring. No new software or changes have been made to my PC other than Avast's updates, so I'm starting to suspect it could be something to do with Avast.

[Maskulo]

Same problem here

Last night I (properly) unistalled Avira, re-booted and finally installed Avast free. This morning I can't access Windows: after writing my password at startup, I get the "Unauthorized Windows Change" message and I'm redirected to a Microsoft web page that fails to load.

System info: Windows Vista Ultimate 64-bit; Avast 6.0.1091 (virus defs 110502-0); virus free.