Avast 4.8 Home Edition - Update Problem

[x86]

Hi all.
I've a problem during the update of Avast virus database, seem that Avast client on PC is not able to connect the server.
In log file the last row is:
Err:Cannot connect to sl207.avast.com (75.126.130.174:80)..
I've tried to switch-off both firewall (Zone alarm and Windows), both the problem is present again.
Avast runs over a WinXP + SP2 operative system and I've the read\write access to disk when avast is installed.
Someone can help me ?   

Thanks in advance.

[DavidR]

You should only have one firewall enabled and that should be ZA as it is marginly better than the XP firewall.
 
Does it allow avast.setup internet access ?
- If it does delete the entry for it and do a manual update, this will force the firewall to ask permission again.

[Eddy]

Are you sure you have only software firewalls? Many routers and/or modems nowadays have a firewall build in.
Are you using a proxy server?
Did you try a manual update?