It will likely be a result of the limits the sampler engine can transpose samples to.

Thing is, it is VERY likely that it is also WAY outside the natural range of the instrument you are trying to emulate. Just because the keyboard goes up 76 notes doesn't mean that the sound it is emulating does...

If you have any decent sound editing, you might be able to edit it to include a simple synth sine wave or something like that to extend it's range (obviously, the samples can't go that high for this sound) to cover the wraparound section, but better would be to realize that natural sounds have a natural range. Play withing them, and not only will you avoid the problem in the first place, but your playing will sound FAR more authentic, too.