Go to apple menu, Software update & update to the latest. There are Java updates. Also, do a safe reboot & repair permissions after doing the update.

It might also be worth doing this: Tip: Purge the Downloads Queue! (click on blue link) as it will help freshen up LW. Also keep your number of shares below 2,000

It's also a good idea to leave LW to settle for 10-15 mins before using. And try not using the Find Souces/Resume button on many files at one time. If you use it, just use it on 1-3 at a time. Otherwise it tends to stress LW & the system & apple's Java unfortunately tends to not cope well with it. In any case, it's much more effective to search the files again. You can control click the file & choose search for ...