preview thumbnails in posts

I have just recently installed the tumbnail excerpt plugin which i think is pretty great. now i realized that it completely messes up my “featured” section on the page. according to the plugin how-to, it looks for posts with information in the excerpt field, and then grabs the first picture from the post, scales it down and displays it.

unfortunately it also does this with posts where there are no entries in the excerpt field which ends up in messing up my featured section. the featured section is this flash news rotating kinda thing which displays a big picture with some text right next to it plus a “continue reading” text.

does anybody know how i can tell the plugin to only use certain categories with the thumbnail preview?

the plugin itself can be found here