Windows 2003 Firewall

I got a Windows 2003 Standard Server with a web site on port 80 and SSL on
port 443. The server is in a WebFarm with another server who have the same
WebSites and configuration. The firewall is activated on one server only for
testing with the port 80 and 443 open. (I use SCW to create the firewall
policy) After a certain time, 10 or 15 minute, the server with the firewall
start logging in the firewall log packet drop on port 80 and 443 but they are
open to everybody in the configuration. The instant I remove the firewall
everything start working perfectly. I check the open ports and they are all
in the firewall configuration.

Any idea about the problem ?
Thank you

Sebastien