Have you allowed LImeWire full access through your firewalls? Check to see if there's a brick wall in front of the globe icon in LW. If so, see this thread for some help:
Connection problems? Check here first!. It's possible to be able to search and download on LW even if you're firewalled, but I makes it almost impossible for someone else to upload from you.
If you still have problems post back with your details:
System details - help us to help you