Static NAT & Duplicate IP Address

[CWJ2001]

Hi I am having a problem with Static NAT translations on a 1712 Router. When I do a static NAT trnslation to an IP in my LAN (as a test a PC) the IP address of the PC becomes a duplicate IP address on the Network. With the same config on a 1605 I have no issue. The strange thing is that the IP address is still pingable on the NAT router even when the PC its natting to is disconnected from the network.

show conf
Using 1117 out of 29688 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname VWNat1
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$4OUC$JAHlsM.Kei2GsCNcwwc8w.
enable password supp0rt
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
no aaa new-model
ip subnet-zero
no ip source-route
no ip cef
!
!
!
no ip domain lookup
no ftp-server write-enable
!
!
!
!
interface Ethernet0
description VW Lan
ip address 10.232.236.2 255.255.255.224
no ip proxy-arp
ip nat outside
half-duplex
!
interface FastEthernet0
description Harris LAN
ip address 10.128.16.5 255.255.255.0
no ip proxy-arp
ip nat inside
speed 100
half-duplex
!
ip nat pool impact 10.232.236.10 10.232.236.10 netmask 255.255.255.224
ip nat inside source list 1 pool impact overload
ip nat outside source static 10.232.236.4 10.128.16.7
ip nat outside source static 10.232.236.3 10.128.16.6
ip classless
ip route 0.0.0.0 0.0.0.0 10.128.16.254
ip http server
!
access-list 1 permit any
!
line con 0
line aux 0
line vty 0 4
password supp0rt
login
!
!
end

VWNat1#