What version of Limewire do you have & where did you get it? What are your computer specs? Are you an adult or a student or running it from home do you have permission to use P2P? And, if you're running it from home, check to see if someone hasn't locked you out of Limewire. or, you dont have your SP2 settings, set to enable Limewire, P2P downloads through, & check your firewall settings to make sure you're configs are correct.

Sounds like someone is preventing you access to Limewire, if that's not the case then, Im not sure whatelse could be preventing you from access it. Browse the forum stickys while you're at it and see if this has come up for PC's running Limewire.

check for virues/trojans/worms etc. do a system scan. check your computer to make sure nothing has gotten infected. or follow Grandpa's advice and check the version of Java you have.

also, what do you have the Limewire licence set on? Tweak your limewire settings to accept downloads.