ERR_EMPTY_RESPONSE in admin for Themes and Plugins

Hello,

In the admin control panel got this error ‘ERR_EMPTY_RESPONSE’ when I want to change THEME or PLUGINS settings.

I’ve tried these to solve the problem:

1> ftp: rename ‘plugin’ folder into ‘plugin-old’. This result into an overview of no plugins. So the ‘ERR_EMPTY_RESPONSE’ disappeared, but there are no plugins available, and when I hit the ‘new plugin’ button, it shows the error again ‘ERR_EMPTY_RESPONSE’

2> ftp: I renamed the theme ‘twentythirteen’ to ‘twentytwelve’. This works at the front end of the website, but when I try to switch theme in the Control Panel, I receive ‘ERR_EMPTY_RESPONSE’.

3> network internet settings> This problem occurs on anny other browser (Chrome, Opera, FireFox, Safari, IE) and it occurs on my Mac or any other laptop. I’ve done DNS flushes, cleared all caches and also reset my router.

4> I’ve also renewed the .htaccess files.

5> My hosting http://www.easyhosting.nl doesn’t have a clue. There are no harmful files of any kind on the server and this problem starts even with a fresh install of 3.7.1 via DirectAdmin, server info below.

Do I have to refine any steps above? Look forward for your help.

==server info:
Processornaam Intel(R) Xeon(R) CPU L5410 @ 2.33GHz
Vendor ID GenuineIntel
Processorsnelheid (MHz) 2333.298
Processornaam Intel(R) Xeon(R) CPU L5410 @ 2.33GHz
Vendor ID GenuineIntel
Processorsnelheid (MHz) 2333.298
Processornaam Intel(R) Xeon(R) CPU L5410 @ 2.33GHz
Vendor ID GenuineIntel
Processorsnelheid (MHz) 2333.298
Processornaam Intel(R) Xeon(R) CPU L5410 @ 2.33GHz
Vendor ID GenuineIntel
Processorsnelheid (MHz) 2333.298
Totaal aan geheugen 8054144 kB
Vrij geheugen 1265484 kB
Totaal swap geheugen 4194296 kB
Vrij swap geheugen 3735868 kB
Systeem uptime 192 days, 5 uren en 15 minuten
Apache 2.2.22 Draait
DirectAdmin 1.44.0
Exim 4.76 Draait
MySQL 5.5.14
Named 9.8.2rc1
ProFTPd 1.3.3e
sshd Draait
dovecot 2.1.16
Php 5.2.17