createMovieClip, onRollover - Not Working

Hi everyone,
I’ve run into a slight problem, ironically, while going back and revising my XML PhotoGallery tutorial. Here is my code:

function thumbnails_fn(k) {
_root.createEmptyMovieClip("t"+k, this.getNextHighestDepth());
thumbMC = eval("t"+k);
thumbMC.loadMovie(thumbnails[k]);
thumbMC._y = 290;
thumbMC._x = 10+105*k;
trace(thumbMC._name);
thumbMC.onRollOver = function() {
trace("HI!");
};
}

The variable k simply receives the total number of images in the XML file. Using loadMovie, I can get the images to display without any problems with the correct spacing also.

Yet, the thumbMC movieclip is unresponsive to my rollover code. The movieclip acts just like a movieclip as opposed to a button. Strangely enough, a similar movie using attachMovie works.

Can anyone point me in the right direction? Does it have to do with my “_root.” call I used earlier?

Thanks!
Kirupa =)