ISP is internet service provider - just the company you pay for your internet access.
Do this test & see what result you get
http://www3.limewire.com:6346

Have you made sure your firewall's set up for LW? There are instructions in the link 6_pac gave you & also here
Firewall setup

Your modem supports UPnP, so you should enable it within the modem & also tick that option within LW's tools > options > advanced > firewall config & then 'apply'. If you're not sure how to enable your modem's UPnP, there's info here
http://subscriber.communications.sie...UG_English.pdf

The modem also has an internal firewall, so maybe you'll have to use port forwarding. Try these other things first though! If they don't help then you can look at port forwarding next.