Hi,
I installed a fresh copy of latest Avast Free antivirus, but I can’t update definitions or program itself.
I get the “Invalid file signature. Setup will terminate.” error. What should I do?
Thanks!
i’m experiencing the same issue 
Any advice?
Try an Avast Repair - Avast 2016: Repair and reset Avast Antivirus - https://www.avast.com/faq.php?article=AVKB204#artTitle
Repair Avast:
Control Panel> Program and Features (Add/remove program)>Select Avast> Select Repair. Reboot when completed
https://www.avast.com/faq.php?article=AVKB204
If Repair doesn’t fix the problem, try the following:
Clean Install of Avast:
https://goo.gl/4Ptzkf
Doesn’t work either.
I tried that many times as well as Windows reinstallation.
I cannot uninstall / change avast at all. I am running Win 7 64 and a week ago suddenly was no longer covered by Avast with the notice that I need to turn on Avast (I never turned it off in the first place). When i try to Uninstall Avast as per the instructions above I get the popup "Setup is already running. Please try to start the setup later. This may be because i d/l’d the latest version of Avast and tried to install it hoping it would overwrite what ever was stuffed up. I cannot terminate the operation - get message “access denied” Where tf do I go now? This is the first crap i have had with Avast in some 7 years!
Colin
Strange, It works now…
I use it since 2010, love it!
Thanks all!
You’re welcome.
After using the avast clean (the only way I managed to unfreeze and ditch the old avst), reinstalled from scratch and now working - by the way f8 does not work to get into safe mode with win 7n, you have to go via setup (f2) and then boot secure.
You simply need to allow the avastclear tool to boot into safe mode.
It does all the work for you provided you allow it to do it’s job.
If what you say is true then YOU have to change the instructions!! They were to put Avastclear onto the desktop, close down windows, boot into safe mode, then only run Avastclear!! So explain how you do that and then let avastclear reboot in Safe Mode???
Hello, I’ve tried this procedure 5 times or more (get avastclear.exe and install avast_free_antivirus_setup_offline.exe, disconnect from the net, uninstall, avastclear in Windows safe mode, restart, install offline version, restart).
Never worked for me. There something still on the computer that the procedure can’t clear.
My Avast still have the message “File uat.vpx has invalid signature when installing or updating.”
I’m unable to update the software nor the signature database.
The installed version of Avast find no virus or malware. Neither Malwarebytes.
I’m actually running on Windows Defender.
What to do now? :o
[b]IMPORTANT FOR THOSE WHO DO NOT UPDATE AVAST.
If you get the error that says “File signature is not valid. Installation will end” As much as giving the button update 3 or 4 times usually catch a server that works.
I am like I am updating the avast when it does not update, at worst it says 2 or 3 times that of the signature but to the 4º update.
The servers (only some) are bad and when they download a file called uat.vpx gives the error, but as I say ONLY IN SOME SERVERS, if they insist 2 or 3 or 4 times should update without problems.
They will tell me if it works (well to me if it works)
Greetings to all.
PS: and forgive the spelling because using google translator I do not know if this will be very well translated.[/b]
Sorry, i’m french and not speak english
J’ai le même problème sur plusieurs ordinateurs donc j’ai vite compris que le problème venait des serveurs Avast…
Après avoir insisté une bonne cinquantaine de fois sans succès j’ai cherché une mise à jour manuelle et ça marche parfaitement
Thank you 
But I bring a solution, that does not have sense to post it only in the French section…