Passwords on remote phones rejected after cable to fibre connection upgrade

Asterisk 1.4.26.3
centos 5.4
freepbx 2.6.0
Linksys WRV200 Router

I helped a friend upgrade the connection his asterisk box uses today from a cable connection to 3gb fibre optic link.

After the switch none of the remote phones would connect. The log says their passwords are bad. ??? Nothing changed on either side and all in-house phones are fine.

[Jan 23 20:42:33] NOTICE[3171] chan_sip.c: Registration from ‘"EcoSales"sip:[email protected]:5060’ failed for ‘yy.140.120.xxx’ - Wrong password
[Jan 23 20:43:19] NOTICE[3171] chan_sip.c: Registration from ‘"EcoSales"sip:[email protected]:5060’ failed for ‘yy.140.120.xxx’ - Wrong password

The yy and xxx are just used to hide my IP.

Has anyone ever seen anything like this???

At 1st I thought it was a router issue but I only changed the wan address, gateway and dns servers.

Help,…anybody

Does the major increase in speed require some kind of change to a timing setting somewhere???

I’m stumped and desperate.

Did the change of link cause any IP address changes (e.g. that of a border router?) Are any old addresses coded into any asterisk config files (grep for them)?