I presume you are using LW 5 on Leopard. Some others have had a similar issue, never been able to find the exact cause. You are using a macbook?
One thing to consider, when LW first opens you need to wait for it to open properly (no spinning circle beside the Library icon on left side of LW's interface.) This might take considerable time.

Alternative is to downgrade back to LW 4. See more about that here http://www.gnutellaforums.com/downlo...downloads.html

You may wish to report your issue as a Bug here LimeWire Forums
I noted this issue at the LW Beta forums & nothing ever happened about it. The JIRA will have them take more notice.