Using Firefox 1.5 and the Tabbrowser Preferences plugin on Gentoo Linux, WordPress 2.0 RC3.
I'm having a problem when writing a post. I made a mistake when I put the html for a link into my post which I didn't catch until after publishing. I went back to edit the post and the editor automatically formatted it as a link rather than html. I expect all this is part of the nifty rich editing, so I clicked the html button and got an error:
tinyCME object reference not found from popup
and my location changes to wp-includes/js/tinymce/themes/advanced/source_editor.htm
I disabled the firefox extension tabbrowser preferences and still got the error so tweaked my firefox tab settings. I normally set "Force links that open in new windows to open in: A new tab" so I disabled this, and the html link works fine.
This is not a WordPress issue per se, but something Firefox users should be aware of when making use of that feature in WordPress.