After transferring some web sites to new server, most of them (joomla, and similar php applications) stopped working because of errors like "fatal error: out of memory"
After research, it turned out that reason is too low RLimitMEM parameter in httpd.conf. It had value that were set by "Memory Usage Restrictions" script from cPanel Apache Configuration.
Most of them try to increase the php memory limit.
-Remove the RLimitMEM directives in httpd.conf