Somehow the LW installer is messed, or is reading the destination folder(s) as "locked" or protected. Try a Sherlock search for "locked" folders (click the "edit" button beside the "options" button on the Sherlock search window to bring up the option to search for locked files/folders).

Another possibility is to download a different installer, like the latest beta version from the bottom of your Pro page or the free one from here http://www.limewire.com/english/content/beta.shtml