I hope you downloaded LW from the official website: http://www.limewire.com/english/content/download.shtml ?
To check for firewall see: http://www.gnutellaforums.com/showth...threadid=26886 & see what your result is.
Make sure you have LW properly configured for a dial-up connection. What platform & OS version do you use? Make sure you don't overdo your bandwidth. Don't simultaneously use 2 p2p apps & keep other net use to a minimum such as browsing & dwnlding from sites (eg-updates) whilst using LW.