We had limewire working fine for about 6 months and then all of a sudden it searches for an audio file, any audio file and nothing comes up. All the network and firewall settings seems to be fine.

The client is running windows xp and using 3G to connect.

Is your LW connected properly (all green/blue connection bars)? If LW is connected, try the fixes below...they're things that have helped other people.

1. In LW go tools > options > searching > basic & check whether the 'show license warning' box is ticked. If it's ticked , untick it > Apply > ok...see if that makes any difference.
LW 5 users, check this link for info about the license warning: http://www.gnutellaforums.com/338001-post3.html

2. Problems with the search

3. Delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will change all of your settings within LW's options, you'll have to go back through afterwards & reset things to the way you like them.
Vista users: LimeWire Pref Folder in Vista

4. Disable all options (TLS, DHT, UP capablilties) within LW's tools > options > advanced > performance.

If none of those things help, run the condi program mentioned in this thread (click on link) & send the log file to mrogers: http://www.gnutellaforums.com/335648-post19.html
There's more info about condi here: Connection Diagnostics - LimeWire

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If LW is not connected, try the fixes here: If LW Will Not Connect
If nothing there helps, post back with your system details