I tried to move our BM server that is currently only set up to do Proxy
but will do NAT from one public IP address to a new Public IP address.
The server works fine on the old ISP.

Server was updated to NW SBS 6.5 SP5
BM 3.8 SP 4
Proxy.cfg from C. Johnson web site
Most settings used from tuneup.ncf

Server worked no problems still on old ISP.

Proceeded with move

Before I tried the move I tested with my laptop using the new public IP
address and found that the new ISP was working. everything worked fine
when I plugged in the laptop. (I could down load surf the web etc etc.)

Start of Migration to new IP

1) I bound the public nic to the new ip address with new subnet mask.
2) I changed the Default gateway to point to the router supplied by the
new isp
3) Change DNS to point to new server
4) rebooted server
5) Could not ping public address in the server (as I had not changed the
filters this was to be expected. Therefore I could not ping Gateway
6) Unload the filters Could ping public address but still could not ping
DF - Gateway
7) Plugged Laptop back in (with same IP address as server) removed
server from Public network. The laptop worked successfully.
8) Rebooted server again and checked settings. Was not Loading BM at
this point. Removed the filters and still could not ping Gateway

At this point I became stuck.

Can anyone help what have I missed?

Is it because I used the same IP address and the Router Cached my
laptops Mac address? Or is there something else