OS: Windows 7 x64 Home Premium
Other Security Software: COMODO Firewall (Only firewall)
Bitdefender Antivirus Free stops updating if the internet connection is interrupted during the running session of the computer. (e.g. Router is powered off). It will update in the next reboot of the computer. I don't know if it will happen with Windows Firewall as I do not encountered this scenario during the time I'm using Windows Firewall.
