Any Mac owners out there who can help me?

I 'm having trouble getting midis to play. The sound is coming through, but the music is garbled to the point that the tune is unrecognizable. It's almost like the chords are not in sync with the melody. They used to play just fine, but now, every time I try to play something that is in midi format, it comes out garbled. RealPlayer works just fine, it's just the midis that won't play properly anymore. I've tried throwing away all of my Quicktime, and starting over again, but that didn't work.

Any help would be most appreciated.   KT