Avast Internet Security 6 blocks LAN addresses

I recently purchased Avast 6 Internet security. I had been using the free antivirus and a separate firewall program and I wanted to support Avast and integrate the two programs. The install went fine, but I was unable to access the network or the internet. When I ran ipconfig /all I received the message that there were no bound adapters so I could not release or renew the IP addresses. When I uninstalled the program and reinstalled the previous ones the problem went away - I could see all the adapters and everything worked fine.

What went wrong, and how can I fix the problem as I would like to use the program?

Thanks for the help.

Which are the previous ones?
Did you use specialized tools to remove remains of old antivirus/firewall installations?

I was using Comodo Firewall and the Free Avast 5.1 antivirus. I removed the programs using the standard windows add/remove software procedure and then rebooted before installing AIS 6. I did not use any special tools and when I reinstalled the original programs everything went smoothly.

Thank you for your help.