Comodo can block outbound connections whilst it hasn't fully set up and this sounds like what is happening, otherwise if it was fully blocked it wouldn't work for manual updates either. I don't know who you can restrict this on comodo (I don't use it), but you could delay the update check in avast and that should give comodo time to get fully established.
You need to edit the [InetWD] section of the C:\Program Files\Alwil Software\Avast4\Data\avast4.ini file and add the following line (depending on your connection type enter one or other of the Bold lines below):
Dial-up connections, add this line: RASWaitSeconds=120
Broadband connections, add this line: AlwaysConnectedWaitSeconds=120
[InetWD]
AlwaysConnectedWaitSeconds=120
Or
RASWaitSeconds=120
The figure is seconds and the above equates to two minutes, you could try that and adjust upwards if required, 180, 240, etc.
Hi,
I think I did not explain correctly.
The error pops up not after I boot up, but during the day, which means after my PC is on for hours.
On the other hand, the update works correctly when I boot up.
For example:
If I boot up my PC at 09.00 am, I get the Avast update without any problem.
Often, during the day you get another update, for instance at 15.20 pm, there I get the error.
I enclose a snipped of the warning.log of the last 3 days:
20/01/2008 16.04.06 1200841446 SYSTEM 1676 Function setifaceUpdatePackages() has failed. Return code is 0x00000426, dwRes is 000004C8.
20/01/2008 16.04.06 1200841446 SYSTEM 1676 An error has occured while attempting to update. Please check the logs.
21/01/2008 23.12.23 1200953543 SYSTEM 1644 Function setifaceUpdatePackages() has failed. Return code is 0x00000426, dwRes is 000004C8.
21/01/2008 23.12.23 1200953543 SYSTEM 1644 An error has occured while attempting to update. Please check the logs.
22/01/2008 13.06.48 1201003608 SYSTEM 1652 Function setifaceUpdatePackages() has failed. Return code is 0x00000426, dwRes is 000004C8.
22/01/2008 13.06.49 1201003609 SYSTEM 1652 An error has occured while attempting to update. Please check the logs.
22/01/2008 17.13.25 1201018405 SYSTEM 1652 Function setifaceUpdatePackages() has failed. Return code is 0x00000426, dwRes is 000004C8.
22/01/2008 17.13.25 1201018405 SYSTEM 1652 An error has occured while attempting to update. Please check the logs.
23/01/2008 14.25.33 1201094733 SYSTEM 1640 Function setifaceUpdatePackages() has failed. Return code is 0x00000426, dwRes is 000004C8.
23/01/2008 14.25.33 1201094733 SYSTEM 1640 An error has occured while attempting to update. Please check the logs.
Hope I made myself clearer

Regards
Alex