If you are experiencing the same problem, which I find hard to believe.
What OS are you using (pachavaillaz didn't say what his OS was)?
What version of avast are you using (pachavaillaz was using the 4.6.623 version)?
Why not try the same solution, if indeed your problem is identical, a manual program update and delete the entries in the hardware menu?
This is pachavaillaz.
The problem came back but only half of it. Now only the avast Mail scanner "hardware" wants to be installed at startup. Avast Mail scanner software works. I am using Thunderbird version 1.0.2 with Avast on-access scanner enabled.
Windows XP Home SP2
Avast version 4.6.652
Zone Alarm version 5.5.094.000
I did some more research and found out that if you uninstall the Mail scanner entry (which has a question mark in front) in control panel-system-hardware then do a restart ("restart" button in shut down screen) the problem stays away (no hardware install question at startup) but if you do a shut down ("turn off computer" button in the shut down screen) then at startup the system wants again to install Mail scanner hardware.
Hope anybody can make sense of it.
Pierre
UPDATE
I finally found a work around:
instead of uninstalling the Mail scanner entry (which has a question mark in front) in control panel-system-hardware I only DISABLED it. No nagging message of the install wizard wanting to install the mail scanner "hardware" at startup.
Pierre