No sound, Music has blank spot during play, MacMini OSX 10.5

I have noticed a glitch in the audio while playing tracks in mixvibes Cross 1.2.5 on a mac mini 1.83ghz intel core2duo with 1gb ram. I am usually running iTunes and sprint smartview/firefox for internet. When these songs play in iTunes, there are no glitches. When I play at weddings, ( i use vinyl for house music gigs, mixvibes for weddings.) I do not use any control vinyl. I just use the program to output the audio streams unless someone pays me enough to bring the turntables out.
**The funny part is I can see the blank spot on the track overview strip that shows the wave form. When the blank spot hits the playline, sure enough, it glitches to no sound. I thought it was because I have made a couple copies from my original hard drive and there were errors on the drive. Then I realized it happened on a track that I just downloaded from iTunes! Now I know it can not be from having old data.
Anyone have ideas about what is causing the glitch?
**The funny part is I can see the blank spot on the track overview strip that shows the wave form. When the blank spot hits the playline, sure enough, it glitches to no sound. I thought it was because I have made a couple copies from my original hard drive and there were errors on the drive. Then I realized it happened on a track that I just downloaded from iTunes! Now I know it can not be from having old data.
Anyone have ideas about what is causing the glitch?