Adding Inline Style to WP Generated Image

I have a wordpress site that I have been working on and I am running into an odd problem.

On any of the category pages, here is an example link here, I have the category set up so that when you mouse over an image, it enlarges using css.

However, if I set the featured image for that particular post the mouseover only shows the same thumbnail. Not the enlarged one.

I have narrowed it down to this line of code in defaultindex.php where WP is generating the image for me but I do not know how to create an inline style to force the image to enlarge.

<b><?php print_thumbnail($thumb, $thumbnail["use_timthumb"], $titletext, 200, 200, 'large'); ?></b></a>

Anyone have any thoughts on this and how I can make this happen?

Thanks

paul