What are the errors in your web server error log?
Sorry but I disable error log 🙁
I have the same problem.
Here the errors from the web server:
[Sun Jul 21 20:06:49 2013] [error] [client 2.39.192.106] Premature end of script headers: minify.php, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:49 2013] [error] [client 2.39.192.106] suexec policy violation: see suexec log for more details, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:43 2013] [error] [client 2.39.192.106] Premature end of script headers: minify.php, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:43 2013] [error] [client 2.39.192.106] suexec policy violation: see suexec log for more details, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:18 2013] [error] [client 2.39.192.106] Premature end of script headers: minify.php, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:18 2013] [error] [client 2.39.192.106] Premature end of script headers: minify.php, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:18 2013] [error] [client 2.39.192.106] suexec policy violation: see suexec log for more details, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:06:18 2013] [error] [client 2.39.192.106] suexec policy violation: see suexec log for more details, referer: http://www.---.com/siti-internet/siti-aggiornabili/
[Sun Jul 21 20:04:54 2013] [error] [client 62.149.140.106] PHP Fatal error: Call to undefined function get_wp_user_avatar() in /web/htdocs/www.---.com/home/wp-content/themes/fawola/content-post.php on line 89
I’m suspecting that my server doesn’t like the row Options -MultiViews
into /wp-content/cache/minify. In effect this folder is empty as if the plugins didn’t manage to write anything in it.
Any suggestions?