asterisk users - May 2003 - register with outbound proxy from behind nat for freeworlddialup etc.

Hi,
I've posted a simular message little over a week ago so sorry for
reposting. I need to register to freeworld dial up from behind a nat.
Using the xten software sip client works fine but with asterisk I don't
know how to do it. Last time I posted I got different responses. Some
saying I can't register with an outbound proxy from asterisk others said
they have done it. If it is possible please somebody send me a sample
config. If not, would it be possible to integrate it into asterisk? I
don't konw how to program so I'm really sorry I can't do it myself.
But
maybe some of you more skilled programmers can make this possible ;-).
I think the possibilities would be great. There are more and more
services like freeworlddialup (http://www.pulver.com/fwd/index.html)
that could help voip to break trough for private users and I'd just hate
not to be able to participate just because I'm behind a nat and using
asterisk when other people with a regular sip client don't have this 
problem from behind a nat. If anybody could help me achieve this I'd be 
very thankfull and I know of quite a few others that would be, too.
Anyway, here what I'm exactely trying to do. My asterisk system is
behind a nat and I'm trying to register with freeworld to place and
recive calls. My setup works fine if my * box dials into the internet
directly but from behind the nat if I dial out the other person can't
hear me, and I can't be called at all. I've tried for hours with tons of
combinations, registering to fwd.pulver.com and fwdnat.pulver.com (same
as 192.246.69.247) but no luck.
I'll atach my sip.conf and extentions.conf and the way to configure the
xten (www.xten.com) free sip client at the end. 
Thank you very much for any help or feedback!
Regards,
	Oliver

sip.conf:

	[general]
	register => 34477:xxxx@fwd.pulver.com/34477
	;register => 34466:xxxx@fwd.pulver.com/34466
	;register => 33537:xxxx@192.246.69.247:5082/33537

	[fwd]
	reinvite=no
	canreinvite=no
	nat=yes
	type=friend
	secret=xxxxx
	username=34477
	host=fwd.pulver.com
	;host=fwdnat.pulver.com:5082
	context=incoming-fwd
	callerid="Oliver Brandt" <34477>

extentions.comf:
	
	[freeworld]
	exten => _X.,1,Dial,SIP/${EXTEN-1}@fwd|60|rT

	[incoming-fwd]

	exten => _X.,1,SetCallerID,8${CALLERID}
	exten => _X.,2,Goto(extern,111,1)

Configuration for the xten sip client:
	
	"Display Name:"  the name you want others to see
	"User Name:" 16000
	"Authorization User:" 16000
	"Password:" is: (your_password)
	"Domain/Realm:" is: fwd.pulver.com
	"SIP Proxy:" is fwd.pulver.com:5060

	Left Click on the "SIP Proxy" button
	and for
	"Out Bound Proxy:" use: 192.246.69.247:5082