This has been pasted from TruStarWarrior's new "problem compilation"
It may or may not help, but good luck
19Q. I get an error message saying that there was “No incoming port found.” How do I fix this?
19A. Go to Tools > Options. On the Network tab, there is section labeled “Listening Port.” In this section, there is a field called “Listen on Port” that should have the port number “6346” typed in. Other acceptable numbers are 6347, 6348, and 6350, but this is not an exhaustive list by any means. If a port number is already entered correctly and you continue to receive this error message, you can try downloading an alternate version of LimeWire 1.6. It is designed to let anyone having connection problems connect to the Gnutella network when using versions 1.5 and 1.6. Click on this link to download it:
http://www9.limewire.com/download/LimeWire16d118.exe