Check that iTunes integration is still enabled in Preferences>iTunes.
Occasionally You will find the integration fails to work, particularly if you are working Limewire particularly hard, or it has been running for over several hours. It is a good idea to reboot after about 24 hours to clear the Virtual memory that Limewire is notorious for hogging. Rebooting has always got iTunes integration working again for me.
Another thing that might help is to delete your Limewire preferences folder in Users>Your Name>library>preferences Only do this while Limewire is FULLY closed and by doing it you will need to reconfigure all your Limewire preference setting next time you start it, so don't do it unless you have to
Let us know if you still have problems, and if you do tell us a bit more about your set up.. Memory, processor size, free space on start up disc, and OSX version.