new ISP? Are your accounts on the old ISP so now no longer in existence to connect to?

I have a POP3 account under my own domain. Servers were mail.livemail.co.uk and smtp.livemail.co.uk. I also have a gmail iMAP account. Neither of them are accessible through my new router. It's the same ISP with an upgraded service and a new router. I can access my gmail through the browser on my desktop pc through the new router, so the router isn't the problem. The ISP techs gave me some new settings - new mail servers and port settings, but the new settings don't seem to have stuck - Tbird is still trying to access the old livemail server and failing. I've been into 'account settings' in Tbird, entered the new mail servers. Restarted Tbird. The new settings are there in 'account settings' but Tbird is still trying to handshake with the old mail servers. There isn't a 'save' button in the server settings page. Any thoughts?