Avast 7 & 8 Corrupts downloads

Windows 7 Home Premium 64bit Asus laptop: Have had several problems with downloads and updates being reported as corrupted. I can download them on an XP desktop, running Avast with no problems. Today Firefox wouldn’t update so I downloaded the update separately on the Win7 laptop. File wouldn’t open …reported corrupt. I turned off avast shields for 10" deleted the corrupt download and downloaded the same update with avast off…this time the download installed with no problems. I updated from avast 7 to 8 and repeated the experiment…same result. Apparently, on some Win7 systems, Avast shields may corrupt downloads.

Hi ,i have also a ASUS win7 Pc a several years. i did run avast on al my pc at home without problems and suddenly my ASUS laptop failed with AVAST.protection . nothing of wat i did resulted in a restart of avast. SO it stays unprotected.IS it a problem that my laptop did not recieve updates from the windows platform sinds a few year?I did it because it need every time a lot of datavolume of my quota.

Newbie Reply/Inquiry on an “old” post: Can I simply Forget about my Windows KB976932 SP1 Update?
I’ve tried downloading twice…with no success. I’m pretty sure it’s my Free Avast that is probably slowing-it or completely stopping-it.
I like my Avast (former Kaspersky user) a lot, and don’t want to try and tweak-it simply to Download this update.

Avast does not stop nor does it interfere with Windows Updates installation.

http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_update/windows-update-error-code-80070017-win-7-sp1/1440572d-5737-4fcf-b386-b16f58be48b2