Hello,
well there might be several causes...NDIS filter may interfere with Win Fw, incompatible softwares may cause system hanging, infections may return random behaviors and so on.....so, my first suggestion is:
1) since kav for wks provides you a real firewall, you can disable win embedded fw....if you do not want to do that (or you can't), try to uninstall NDIS filter from your network connection properties, restart OS and check it;
2) run
Getsysteminfo on your machine and check via online parser if your system is hosting incompatible software.
M