A few people have had probs with LW 5 freezing while loading the library (when you see the spinner above the connection bar, does it also spin next to My Library?). Check out this thread from the LW forum: LimeWire Forums

If you've already tried updating Java & deleting the preferences folder, maybe you're better off reverting to 4.18.8 to see whether that works: Get LimeWire for Your Platform - Lime Wire & under Past Releases you'll see a link to download 4.18.8.

If you do want to keep trying with LW 5 - after you deleted the prefs folder, did you have to go through LW's setup all over again? If not, then you need to make sure that LW's completely closed & delete the prefs folder again (deleting it while LW's open has no effect). Or you could try an older version of Java 6: Archive: Download Java Platform Standard Edition (Java SE) 6u5
Just make sure to remove all other Java versions before you install another version. And reboot after the Java installation's complete

Or you can try the latest Beta: LimeWire Forums
Just remember that it's a Beta & so might have bugs