getimagesize(): Read error! with CategoryIcons plugin

I am using the CategoryIcons plugin which can be found here http://dev.wp-plugins.org/wiki/CategoryIcons. My settings appear to be correct as I can assign icons to the categories and my plugin is activated but when I try to inser the code to call the icons into my index page, I get the following error message:

getimagesize(): Read error!

Any idea what’s causing this? I’m sure it’s something stupid that I’m overlooking but I’m stumped right now.