Thank you for the direction, I am going to have to come up to speed on a few things, to work on the advice, but for now
The SPI firewall on DD-WRT machine is disabled
There are no Security Policies in place on the DD-WRT router (in the Security Tab)
DMZ, QOS are disabled
WAN is Disabled
DHCP is disabled
Advanced Routing is set to Router Mode
The Firewall and all other security on the Arris CM is off (for testing)
RoutedwithNAT is on in LAN Settings
DHCP pool starts at x.x.x.05
One other fact I discovered this afternoon is that though DD-WRT has the option to make the uplink port just a regular port when DHCP and WAN are disabled - and according to the wiki on WRT the connection should be lan-lan port, NOT uplink port, I only get internet on the M1 and M2 when the cable from the CM is plugged into the uplink port, not any other port, even though the uplink port is supposed to be just a regular port. So its as if the Netgear is not taking the WRT setting, or the Arris won't recognize a connection to any other port.
Even stranger is WIRELESS connections (droid phone) through the netgear router (diff SSID than Arris CM) will ping through to M2 and it has internet - so its just the two wired machines that cannot see each other;
For completeness M1 and M2 are both running Lubuntu 12.10 and have no security/firewall policies that I know of turned on. I am going to revisit local firewall settings as I can't see anything else in WRT that can be changed. I appreciate the help, the best I have gotten at DD-WRT is "it should work if you followed the tutorial"