You should always keep your old installers... that way, if you have trouble with one version, you can revert back to an older one!
Double check that your XP firewall is configured properly. It's better to configure your firewall than to run without one.
Firewall setup

If your router supports UPnP, enable it & then choose the UPnP option in LW's tools > options > advanced > firewall config. Restart LW & give it a while to settle down (half an hour maybe)... see if that gets rid of the firewall.

Otherwise, you might have to port forward. This should get rid of the firewall & hopefully improve things for you. See the link below for the Ultraline manual, there should be instructions there.
http://www.westell.com/content/sales/7400.pdf

In LW tools > options > advanced > firewall config will show you LW's listening port number. That's the port number you'll need to forward within the router. You'll also have to choose the 'manual port forward' option on that page & enter LW's listening port into the text field.

Most of the time, port forwarding also requires you to set up a static IP address first, there should be something about this in the manual if you need to do this for your model. There will probably also be instructions for this step! If not, see the link below
http://www.portforward.com/networking/staticip.htm