I've been working with the FFT functionality of the Ess library and have noticed some weird spectrum behaviour when playing back an mp3 song using the inputFFT example code from the Ess website (http://www.tree-axis.com/Ess/_examples/inputFFT)

Here is a capture of what I am talking about... I've highlighted the area of interest with a red box:
http://img442.imageshack.us/my.php?image=spectrumpf7.png

the rest of the spectrum looks perfect and responds correctly to the audio, however the section in the red box seems to maintain that 'exponential' curve, and pulses to the lower frequencies like the beat even though its in the 'high end' of the spectrum. Its very odd because there is a fairly distinctive 'cutoff' point where the 'normal' spectrum seems to stop and the curve begins.

Does anyone have any idea what this could be from? Should I possibly just discard the area? or maybe its getting shifted somehow?
Thanks in advance!