FWIW I just solved my issues with the visual editor not displaying…as I mentioned above, my web host had setup phpsuexec on my server, which hosed a lot of stuff. I figured that tinymce just wasn’t fully loading at times, so uploaded a php.ini file to this directory:
wp-includes/js/tinymce
the file contains two lines:
memory_limit = 32M
output_buffering = On
This seems to have fixed it for me. Hope it helps someone else. ??