Wireless connection on Vista

[EnglishMick]

I'm having a problem on my laptop. I'm trying to connect to a wireless network and ie is showing that it can't display the page as i'm not connected to the internet.
In my connections it's showing that i am connected to the network.
When I turn off avast! I can access the internet, but as soon as I turn it back on I'm back to square one.

I'm using windows vista and i'm new to it so i have no idea how to fix the problem, can anyone help? Thanks in advance.
If you need any more info to help, just let me know.

[DavidR]

What is your firewall ?
Does it allow ashWebSv.exe internet access ?
- If it does delete the entries for them and do a manual update and reconnect to the internet, this will force the firewall to ask permission again.