1. Has this only been happening during this session of using LW? If yes, then I'd suggest restarting your comp. If it's not, then I'd suggest you lclena up your system using utility apps & defragging your hdd.

2. Change the location of your LW downld folder. Go to Tools>Options>Saving & choose a new location. You may need to move your files from your incomplete folder to the new incomplete folder.

Are you sure you have admin rights to your computer? If yes then do the give LW the admin rights as in the sugestion in the earlier link.

Even try setting up a new user account. On which you have control over. Try using LW within that account.