I'm going through the same issues on Firefox, Safari, and Chrome. I've had some other suggestions:
Deactivate Plugins (didn't work for me)
Change theme to default to see if it goes away (haven't done this yet)
Below is a post that I tried to follow, but I got lost on the code when I opened it in Dreamweaver. Maybe you'll have better luck...
Good Luck!
And the resolution here:
http://trac.wordpress.org/attachment/ticket/3144/3144-gzipoptoins-tinymce.patch
worked for me. In the file wp-includes/js/tinymce/tiny_mce_gzip.php I changed the line:
if ((in_array('gzip', $encodings) || in_array('x-gzip', $encodings) || isset($_SERVER['---------------'])) && function_exists('ob_gzhandler') && !ini_get('zlib.output_compression')) {
to read this:
if ((in_array('gzip', $encodings) || in_array('x-gzip', $encodings) || isset($_SERVER['---------------'])) && function_exists('ob_gzhandler') && !ini_get('zlib.output_compression') && get_settings('gzipcompression')) {
and that immediately solved the problem: the Visual Editor appeared just as it should.