onEnterFrame prob

Has anyone ever experienced a call to onEnterFrame not completing?

By this I mean, I am calling onEnterFrame on a picHolder movieclip. Inside the onEnterFrame I am fading in the image like:

_root.currentHolder.picHolder.onEnterFrame = function() {
trace(“in onenterframe”);
if(_root.currentHolder.picHolder._alpha <100){
_root.currentHolder.picHolder._alpha +=10;
}

};

The trace statement prints (only once) but the alpha doesn’t get incremented.
What could be happening here?