How to make a loop sound less like a loop

[opethguy81]

Hey everyone, hoping someone can help me out here. I've been recording a metal tune with lots of different tracks of harmonized guitars. Since this was my first project I'd ever done with Ableton, I decided to do it in a loop based format so as to shorten down the time it would have taken to get down the entire lines with punch-ins, etc. I was very happy with the whole experience, except that when the riff restarts itself, you can tell that the loop has ended and restarted. What's even more curious is that there's two main riffs in the song, and this tell tale looping only affects the first riff, and not the second one. I've uploaded this song to lightningmp3 so you can hear it for yourself:
http://www.lightningmp3.com/live/file.php?fid=10252
Anybody have any ideas? I'd definitely appreciate it