Don't know anything about your network situation, but maybe your workstation, where you plug your zaurus into, is itself behind a router, so you have to add another route on the router?
For example you have the following configuration:
Inet <--> Router (192.168.1.1) <--> (192.168.1.2) Workstation (192.168.129.1) <--> (192.168.129.201) Zaurus
Then you have to add the following route on the router (linux syntax):
route add -net 192.168.129.0 netmask 255.255.255.0 gw 192.168.1.2
The gateway of your Zaurus stays as is. (Should be 192.168.129.1, in the example.)
Additionally, you don't need any masquerading on your workstation, if your router already does the masquerading.