Thanks for the great summary.

About the module thing, I only can contribute what I did on the n800 when I sat that up. The modules I built and loaded were these:

ip_conntrack_amanda.ko
ip_conntrack_ftp.ko
ip_conntrack_h323.ko
ip_conntrack_irc.ko
ip_conntrack.ko
ip_conntrack_netbios_ns.ko
ip_conntrack_pptp.ko
ip_conntrack_sip.ko
ip_conntrack_tftp.ko
ip_nat_amanda.ko
ip_nat_ftp.ko
ip_nat_h323.ko
ip_nat_irc.ko
ip_nat.ko
ip_nat_pptp.ko
ip_nat_sip.ko
ip_nat_snmp_basic.ko
ip_nat_tftp.ko
ip_queue.ko
iptable_nat.ko
ipt_MASQUERADE.ko


I have no possibility to check right now but I think that some was build into the kernel in the original config. I hope to find time to try that out over the weekend with the n900.

For the reboot issue, could it have maybe have something to do with the buffers set for nat and how overflows are handled. I just remembered that having many connections in parallel sometimes caused some buffer to fillup and once it was full the effects were some severe hangs on the router. If I recall correctly increasing the buffer size via /proc solved the problems. Just some idea