I installed Firebug too, (thanks for that, batsi) and trace my trouble to the Window.tinyMCE permissions issue. I disabled all of my plugins and get an error in jquery, line 11.
If I’m reading this right, the function seems to be e() in jquery, and this is inside of tb_init(), inside of tb_show(…) in thickbox.js.
“uncaught exception: Permission denied to get property Window.tinyMCE”
When plugins are enabled, the same error manifests elsewhere. Believe it or not, this action worked once. ONCE. (Not ‘once-worked’ ?? )
I updated flash with no effect, too…