In order to search, you must be connected to the network. Since you can't search, LimeWire is clearly not connected.

Are you connected to the internet before you start LimeWire?

Have you tried the telnet test?

telent router4.limewire.com 6346

(You can type this in at the command prompt (DOS box) in most windows variants) - You should get a "gnutella OK" response - this indicates you can connect to the network.

Otherwise - provide full details of Operating system, version of Java, version of LimeWire, internet connection type, any firewall or router.

Mark