"Determining gapless playback information" doesn't end

Hello. Recently I formatted my external HD and deleted all my music from my iTunes.

when I started downloading everything back, I added about 1500 songs to iTunes, and the message "Determining gapless playback information" doesn't stop; it goes into this proccess and it's been days now. the problem is: it gets my HD busy so all my downloads on utorrent stopped. They go like 8 KBs/s, and when I shut down iTunes (this only works by force quitting), the speed goes back to 1 MB/s or so, the normal velocity.