I have a 3 Mbit/sec connection, and I can get 30-100 kB/sec downloads with 10 hosts. Plus, multiple downloads don't slow my speeds down. That only happened when I had dial-up. Have you configured your firewall in Windows?
Control Panel...Windows Firewall...Exceptions Tab
Make sure Limewire is checked (or add LW if it's not there)
Good Luck
Dano