Applescript editor not responding

I did the following script in order to identify itunes songs that doesn't have artwork. It's based on other script that I found in net.

tell application "iTunes"
   repeat with a in every track of playlist "Library"
      if not (exists (artwork 1 of a)) then
         add (get location of a) to (playlist "noart")
      end if
   end repeat
end tell

It seems to be working, it compiles well, and because I can that it in event log windows:

tell application "iTunes"
    count every track of playlist "Library"
        --> 10684
    exists artwork 1 of item 1 of every track of playlist "Library"
        --> true
    exists artwork 1 of item 2 of every track of playlist "Library"
        --> true

But after 4 hundred tracks, it starts to run slowly, and applescript stops responding after one thousand tracks.

I thought that maybe I could be exhausting my mac memory, but in Activity Monitor, I can see that Applescript is consuming 100% CPU and less than 50MB of memory. I'm running macos 10.7.4 on a macbook pro (i7 with 4GB ram).

As you can see my itunes library has 10684 tracks. It's not a small library, but it's not a huge one.

Does anyone has any advice? Or a script to identify tracks without artwork?

TIA,

Bob

Here's what I use. My main suggestion would be to use "duplicate" instead of "add" and then you do not need to get the location of a track. Also you'll see I'm using "a reference to" most things which makes it work faster. I also create the "no artwork" playlist with a time stamp on-the-fly so I can see when I ran the script.

set d to current date
set missingTracksCount to 0
tell application "iTunes"
    set isFixedIndexing to fixed indexing
    if not isFixedIndexing then set fixed indexing to true

    -- make a new playlist to hold the tracks
    set newPlaylist to make new playlist
    set name of newPlaylist to "No Art - " & month of d & " " & day of d & " " & time string of d

    set mainPlaylist to a reference to playlist "Library"
    set noArtworkPlaylist to a reference to newPlaylist

    set trackCount to count of tracks of mainPlaylist
    repeat with i from 1 to trackCount
        set trackRef to (a reference to (track i of mainPlaylist))
        if (count of artworks of trackRef) is less than 1 then
            duplicate trackRef to noArtworkPlaylist
            set missingTracksCount to missingTracksCount + 1
        end if
    end repeat

    if not isFixedIndexing then set fixed indexing to isFixedIndexing

    display dialog "Finished!" & return & (missingTracksCount as text) & " tracks didn't have artwork." buttons {"OK"} default button 1 with icon note giving up after 5
end tell