I'm having a similar problem, here are my specs

Windows: Windows XP Home edition
Router: Paradyne ADSL Router
Firewall: Windows Firewall (With Limewire exempted from the bad programs list)
PC: 512MB RAM
3.2 GHz Processor
Connection Type: ADSL
Connecting From: Home (1 PC)

For the love of God! I've been trying for nearly 4 hours now and I can't get this **** thing to connect!!!