can't update av dataabase

Hi,
I reinstall my xp and install latest version of CIS (tried this several times) and now update don’t work .it always show "update failled,check your network connection. Any suggestion how to fix this?
Virus signature databese version 1157.
I’m using comodo firewall,now CIS, almost 2 years and never had this kind of problem?

I am having the same problem, all internet connections are working, but CIS will not update. I am getting same message also.