John,
I'm not definite if this is the problem, but it may help to specify which
interface to masquerade on:
/sbin/ipchains -A forward -i ppp0 -s 192.168.0.0/24 -j MASQ
^^^^^^^
That's what I currently have in my setup and it works fine.
Hope this helps,
Bernard.
--
Bernard Blackham
dagobah at mad.scientist.com