I've been having this problem as well but I don't use Norton Anti-virus. Limewire will startup, connect, and run for a while without any problems. After running for a couple of minutes, Limewire will cause my computer to lock-up and then nothing will work until I manually restart my computer. I've also had this problem with Morpheus and, just recently, Shareaza. If anyone has any suggestions, I would welcome them with open arms.