I am having a similar, yet WORSE problem. In one of my installations I can not get the image uploader to even open. When you click on the button, nothing happens.
I only have 2 plugins and a few jQuery scripts in my theme. I deactivated all plugins & switched to the default theme, and it still DIDN’T work. I also re-uploaded the JS folder in hopes that the error was there…but to no avail.
Is anyone else using .htaccess to direct a public_html folder/the site root to a wordpress install? I’m wondering if that has something to do with it.