I thought you were using win 98. If you're using win xp then xp SP2 does reduce the no. of simultaneous connections but doesn't explain why you're getting firewall issues.

Is it possible to connect your computer to the dial up to see if you have the same problems? Is the dial up the same isp?

OK actually I thought they stopped making Westell. I notice your connection device can be port forwarded (open a port.) This might be the way to go for you! Do the following steps in order but pay particular attention to setting up the static ip. If you get this step wrong then the entire process won't work after you disconnect the 1st time.
The steps:

1. Set up a Static ip. http://www.portforward.com/networking/staticip.htm

2. Forward a port (try port 6346); instructions here: http://www.portforward.com/westell/Versalink327W.htm (choose the 3rd link 'Port Forwarding for the Westell Versalink 327W', & then find Limewire on the list!)

3. Within LW: Manual port forward instructions & sample image & 2 posts after that.

Have a strong cup of coffee before you begin the process! lol hahaha

Tell us how you go!