[CentOS] Host Machine and Iptables problem

Hi,

I experienced some problems with my VM's and NetworkManager. Then I 
decided to remove NetworkManager on the VM's and the Host machine and 
everything is working well now.

After that I stopped the Iptables on the Host machine and I lost 
external connectivity on my VM's.
The only way that I found that VM machine works again is restarting the 
Host Machine. (Start Iptables service again on the Host didn't work)

I'm using CentOS 6.2:  2.6.32-220.7.1.el6.x86_64
The host's iptables is the default, I didn't add anything.
Why the Iptables is stopping the connectivity of VM when I stop it?

Thanks in advance!