[Serusers] SER + * on same BOX, behind NAT and doing NAT

[maka]

hi all,
I am currently working on the following:

UAC1(10.10.10.15)---(10.10.10.1)SER+*(192.168.1.5)---(.1)DSL

I can connect to the * from UAC1, can call PSTN through asterisk from
UAC1, and SER is ok with registering and proxying SIP msgs between
external (public IP) clients.

I can't however get an external UAC to hear * echo test or call the
PSTN through *.

Any suggestions would be greatly appreciated, cheers;-)