I'm using the list category posts plugin, and can't get the thumbnail_size parameter to work with a given pixel size. The parameter can be a word, but also a size in X- and Y-dimension, as I understand it. Can someone give me an example of how to write this? Thanks.
What plug-in are you using to display the post thumbnails? This one works : http://wordpress.org/extend/plugins/wp-category-thumbnail/. It requires you to use the regenerate thumbnails plugin on existing images, but after you install it the thumbnails will be the size you specify. You might be able to install the regenerate thumbnails plugin to get the current plugin to work. If not try the one I linked to.