Hi, Meteor Slides uses JavaScript for the slideshow itself, but doesn’t add or change any of the JavaScript in the WordPress admin area.
Can you give me a little more information, when specifically do you get this JavaScript error? When you click “Set featured image”, when you click “Select Files” to upload them, or when you click “Use as featured image”?
You are using WordPress 3.0.1 correct? And Meteor Slides 1.3.1?
My best guess is that another plugin is causing this conflict, the easiest way to test this would be to temporarily disable your other plugins and try it again.