I was reading the release notes pertaining to php accelerator http://www.php-accelerator.co.uk/releases/1.3.3/release_notes
and there is mention of a bug in PHP memory handling
"A bug in PHP memory handling causes PHP builds with --enable-memory-limit to believe that memory is already allocated at the start of each request, and for the amount to increase at each request.
The bug exists in PHP 4.2.1, 4.2.2, and probably some or all other releases.
Release 1.3.3 incorporates an experimental workaround for this PHP bug and
can be enabled with by setting the php.ini entry
enable_php_memory_bug_workaround = 1"
"; Enable a workaround for a bug in PHP that can cause PHP to incorrectly
; report that a script has run out of memory. Defaults to 0, i.e. disabled.
; Set to on or 1 to enable.
; NOTE: This is only relevant is PHP was built with --enable-memory-limit
phpa.enable_php_memory_bug_workaround = 0"
Could this be the reason that some sites are/were having problems and others like those on moodle.com not?