How much ram & available HDD space do you have?

The LW 4.11.1 is the new beta. It does have some bugs. You might be better going for the 4.10.9 for the time being. http://www.limewire.com/english/content/download.shtml

I would also highly recommend making sure your LW is using Java 1.5; Setting up Java 1.5

Do you see a brick wall in front of the blue world icon at the bottom of LW's interface? If yes it means you have firewall problems which might be either OSX firewall or your modem/router's NAT firewall; see Connection problems? Check here first! (click on link)