running limewire pro. on-

dell inspiron 8100
xp professional - firewall disabled
speedtouch 330 modem
tiscali 2mb broadband
norton internet security 2005 - firewall disabled
webroot firewall - limewire permitted
java 1.5

limewire will not connect, i get 1 green bar on the connection strength meter for about 15 seconds then it cuts out and a notice informs me that i am either not connected to the internet or i am behind a firewall. since i am connected i can only assume that it is a firewall problem. Does anyone know if either -

(i) my brand of modem has a built in firewall (dont think so but have had a hard time checking and gettig a definitive answer.
(ii)tiscali have changed their usage policy and are blocking me - i have'nt heard anything and simply cannot get through to their support line


Any help would be appreciated, this is driving me nuts