After I upgraded my avast Anti-Virus to 4.8.1296, avast Auto-Update seems to have stopped working on my two machines: a desktop running Windows XP Home and a notebook running Windows Vista Home Premium. The last auto-update was on 1 December 2008. For the last couple of days, I have had to do the virus database update manually. Please help and advise.
Are you seeing any error messages from avast (a red popup window advising an update failure)?
Thank you for your quick response.
I have not got any error messages, and there have been no popups. I had been getting the auto-updates daily until the last program upgrade.
Are you using a firewall program?
If so please consider removing any avast permissions in it and allowing them to be requested again so that any avast program updates are recognized by the firewall.
I have Comodo Firewall. How do I go about removing the avast permissions? Please enlighten. Thanks.
On the programs tab of settings, remove avast entries and try to use avast again. Comodo will ask for permissions, again, then you can allow and save these new allowed entries.
Before that, you could try a manual update, right click the avast ‘a’ icon, select Updating, iAVS Update and see if that works or displays any errors ?
The problem has been resolved. Thanks for all the help.
How? Help us helping the others 
What was the problem/solution, it may help others who view this topic ?
I am also having the same problem. I am running Zone Alarm 8 I have removed all permissions and then allowed them. I am able to manually update with no errors but automatic seems not to be working. 
In fact, I did not do anything, except uninstalling Comodo Firewall and upgrading it to a newer version.
I wish someone from Alwil guide us on this scenario: manual updates work, automatic don’t.
my updates have stopped as well.
.
any help would be appreciated.
…update… did an uninstall and re-install and all is well…
Bump…