No data Received on Popups

Hi there I am having issues with suitecrm in that when I click on an item say in a target list, I want to add an account or contact or lead doesn’t matter which I get the error.
No data received
Unable to load the web page because the server sent no data.
here is part of the url that is shown on the popup

It does however work if i was to select a user instead.
I tried this in the accounts as well to select a contact with same results.

I have tried quick repair, reset permissions to 777 on the cache folder, (i notice some folders within are set to 2777)
config.php and config_override.php are set to 775

any help would be much appreciated.

Hi, Trying to fix whats going on I have tried reinstalling SuiteCRM 7.5.1 with same results, so built a new ubuntu 14.0.4 server Apache/2.4.7 - php 5.5.9 - mariaDB installed versions 7.5.1 and also 7.4.3 but get the exact same results so not sure what is going on, if I use suitecrm demo site everything i am trying to do works.

This is rather urgent so any help would be great

Well I managed to fix the issue, it appeared to be an issue with memcached, so I added -B binary to the memcached.Conf file restarted the memcached service and all was good. I found the error in the apache error.log file.