Adding shortcodes issue

Checked your plugin and it’s light and great. One thing thoug the browser(s) I use it’s an Opera and an Firefox 3.6 wich is old but I like it so much that I’ll probably use it till the last day of his life. On Firefox when I try to add an shortcode, when I click add yes it gets added but the tb_overlay of thickbox doesn’t disspear and I can’t do anything to my article after that.

Is there something I could do to fix that or not? Thanks.

https://wordpress.org/plugins/smpl-shortcodes/