My error log is filled with
File does not exist: /wp-includes/js/tinymce/tiny_mce_gzip.php
However, it's definitely there. Also, the path in the error log is /public_html/wp-includes/js/tinymce/tiny_mce_gzip.php but it should be /public_html/blogs/ then the rest.
I've double-checked and verified that the file is there, and have even reloaded it, but of course the path isn't right in the error log so something is wrong.
However, when I view the source for the admin page it shows the correct path in the source as /blogs/wp-includes/etc.
As a temporary fix I have uploaded the /wp-includes/js/tinymce/tiny_mce_gzip.php directory and file to the root directory of my site, so that it will pick up. But this isn't the best solution in case of upgrades.