can't use dnscache behinde a router

["joeri Belis" <Joeri.Belis@nollekens.be>]

This is my setup

Segment 1 (192.168.1.xx)
Windows xp 
(192.168.1.1 , dns set to 198.9.200.226)
   |
   |
   |
(192.168.249) router (198.9.200.249)
   |
   |
   |
Segment 2 (198.9.200.xx) 
linuxbox 
(eth0 198.9.200.237 = tinydns)
(eth0:0 198.9.200.226 = dnscache)

Ping from windowxp(192.168.1.1) to linuxbox aka dnscache (198.9.200.226)
works, so I assume the route form/to segment 1 to segment 2 is ok

Ping from windowxp(192.168.1.1) using a name (Ex. ping www.yahoo.com)
Does not work. I used tcpdump to see what is arriving on 198.9.200.226
And is see the packet arrive but there is no response back.

Same tests all from within segment 1 work fine.

Any idea where this is going wrong?