Highlight issue with Dashboard buttons


I've just updated my blog here with working fancy text and image buttons...

The ONE thing that is giving me trouble on round image-filled buttons - is some default grey highlighting when a dashboard "button" is pressed. It shows up in the corner of rounded images - I have no idea how to get rid of it- I've succeeded in putting an alternative image into the (simple) button definition - thisis only a problem for image based buttons..

Can anyone help? Once fixed I'll do a much better job of explaining things on the blog and tidying up the CSS and JS.

HELP please.