You connect from work. Do you also connect from home? If from home do you go thru an independent isp or connect via your work's isp? Something is totally blocking LW. And it sounds like a new event. Perhaps from your work that you're not aware about. The isp or your work may have started to deliberately block p2p use. You could try the newest version of LW 4.2.5 else/& try an older version: http://www9.limewire.com:82/download/ & also
http://www.oldversion.com/program.php?n=limewire

I'm rather stumped. But there's something blocking LW that might not have been blocking it before. How about your own personal firewalls - have you double-checked them? http://www.limewire.com/english/content/firewalls.shtml