[Asterisk-Users] strange asterisk issue

[Kiraly Zoltan]

I have the following asterisk configuration (sip.conf) :

[General]
externip=82.79.81.3
localnet=192.168.10.0
localmask=255.255.255.0

[Phone1]
type=friend
host=dynamic
nat=yes
qualify=yes
context=sip
callerid="Phone1" <1>
disallow=all
allow=gsm

[Phone2]
type=friend
host=dynamic
qualify=yes
context=sip
callerid="Phone2" <2>
disallow=all
allow=gsm

[Phone3]
type=friend
host=dynamic
nat=yes
qualify=yes
context=sip
callerid="Phone3" <3>
disallow=all
allow=gsm

[Phone4]
type=friend
host=dynamic
nat=yes
qualify=yes
context=sip
callerid="Phone4" <4>
disallow=all
allow=gsm

I use the following extensions for asterisk (extensions.conf):

[sip]
exten => 1,1,Dial(SIP/Phone1,20,tr)
exten => 2,1,Dial(SIP/Phone2,20,tr)
exten => 3,1,Dial(SIP/Phone3,20,tr)
exten => 4,1,Dial(SIP/Phone4,20,tr)

This Asterisk PBX configuration work with X-Lite softphone. I have more 
X-Lite clients and all use Windows XP.

Phone 1 = Yo2lux (my phone number) - Windows XP box
Phone 2 = Mike - Windows XP box
Phone 3 = Bob - Windows XP box
Phone 4 = Theo - Windows XP box

Phone 2, Phone3 and Phone4 now turned off, only Phone1 PC turned on :

Phone 1 = Yo2lux (Turned on)
Phone 2,3,4 = Mike, Bob and Theo ( This 3 PC now turned off)

I have a strange problem:

I call Phone2 and don't answer. Ok, the pc is turned off
I call Phone3 and don't answer. Ok, the pc is turned off

I call Phone4 and answer (turned off pc). I get an answer from Phone 
number1. But im not registered as Phone1 at Phone4.

Any idea to solve this problem ?

Thank you very much !