[CentOS] NFS and Firewall

Hi Folks,

I'm using VMWare on a Linux Host (CentOS) with a Linux-Guest Sidux).
And I'd like to use NFS.
Furthermore I'd like to use the Firewall in CentOS with this little GUI.
If I activate this firewall then my Guest says "no route to host" on mounting 
nfs.
Firewall disabled -> no problem occurs.
Is there a solution to use firewall _and_ nfs ?
Please, no iptables scripts. 
I'd like to use this small GUI for the firewall.

Thx
Timothy