We have been approached by a client running SugarCRM CE 5.1 and they complain sometimes when they type an URL of their SugarCRM instance, it returns blank screen (Usually mornings).

They resolve it by restarting their VMWare virtual server with Debian and then it works just fine. It is not an Apache issue, the phpmyadmin running on the same server works fine.

Any tips on where to look for a resolution?

thanks,
Jirka