Problem playing ogg vorbis on Clip

I have a Clip w/ v2.01.35 firmware. Covert WAV to ogg vorbis w/ dBpoweramp release 14.1 using ogg vorbis (aoTuV SSE3) codec & quality variable bit rate. Most files sound fine but some have a strange distortion. Difficult to describe - not really a pop or skip but those are the closest descriptions I can come up with. Anyone else run into this? More to the point, anyone know what causes this?

6/2/11 Addendum: I suspect the problem may be w/ the bit rate setting I used when converting to ogg vorbis. Used the highest quality setting. What ogg vorbis bit rates does Clip support?