Already tried but did not work:
- clean install (not re-install)
- switch to twenty-eleven theme
- disable all plugins
- verify correct folder permissions
- verify users have correct database permissions
- changes to wp-config.php to:
- fix the cookie paths (admin, domain, site, cookiepath)
- allow multiple db
- allow multisite
- exclude async-upload.php from mod-security
- switch to Proftpd through cPanel
- fix the login redirect
- many other small modifications to assorted php files which would take too long to list, but which still work fine on my local dev
Upload hangs for a long time in all browsers and fails without error.
In IE, the only browser to post (after 5-8 minutes), I watched the process and saw that async-upload.php is requested, hangs, never makes it, and then is requested again successfully by "JS Library XMLHttpRequest".
After the successful, second request the image finally is posted if I use IE, but no tools (Firebug, Chrome developer tools) in the other browsers have provided any clues. Debug turned on also reveals nothing.
In my local install of WP, the exact same db (except for url, which is changed by a script on upload) and exact same files (with url also changed by a script where it is referenced in the theme css) post quickly and correctly in all browsers.