a) IE is a lousy browser: whenever problems reported here prove to be browser related, it's almost always IE, sometimes Chrome, almost never Safari or Firefox.
b) Which buttons are you referring to? You can edit the post, click "Edit" next to Visibility (in the Publish module), uncheck the option "Stick this post to the front page", click OK, click Update. But you can try a (faster) alternative: go to Posts > All Posts, hover over the post title, click Quick Edit, uncheck the option "Make this post sticky", click Update.