I was having this same issue and tried all of the remedies above, including uninstalling and reinstalling Limewire Pro. It turned out that the problem for me was the gnutella.net file.

Here's the post that helped me:

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Originally Posted by Kath
In XP: enable viewing of hidden and system files go to the Tools
menu in Windows Explorer, then Folder Options, and in the View tab set it to show hidden files and folders and system files.
Once you've changed those setting you can find the
folder "C:\Documents and Settings\Your Name\Application Data\LimeWire". It Might alternatively be at C:\Documents and Settings\Your Name\.limewire with certain LW versions in certain SPs

In Windows Vista to enable viewing of hidden files in any windows folder click tools > folder options at the top. click on that and then view then show hidden files and folders. it is at C:\Users\name you use to login\AppData\Roaming\Limewire It MIGHT also be at C:\users\myname\.limewire Any confirmation of where you find it would be welcome This seems to depend on the version of Limewire you are using.
Another way is to go to Start > Control Panel > Folder Options > Click on "View" tab > Click "Show Hidden Files and Folders

If you find there is no gnutella.net file in the appdata or preference folder, it doesn't matter. Just put the new file in there anyway. It just means that Limewire did not actually create the file itself, which sometimes happens.

Then:

Just click (Do not right click) on this: LimeWire Forums And save (don't open) the file either to somewhere you can find it like your desk top... or, only if you know where exactly to save it to, to that location. You need to register as a member of the Limewire forums to do this. LimeWire Forums
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Hope this helps!!!

ShannonATX