I0m lost and I can't find the way the make my m0n0 works...

I have DSL static IP, and filled the configuration with the following 
parameters... the same that if I set them in one PC, the PC connects to 
internet:

WAN IP address for m0n0wall device: X.Y.Z.100
Network mask: 26 (equals to 255.255.255.192  the one that my ISP told me)
WAN Gateway: X.Y.Z.100.65
DNS: the ones I use

and... I can't ping anything... from mono console, webgui or a client.
Obviously the m0n0 works as DHCP server and the client as DHCP client.

Any hint? HELP PLEASE! I want to be a m0n0-addict! ;)