You may have encountered the following out of memory error while attempting to log-in to your administrative section that is related to a basic PHP setting which defines the memory limit for individual processes:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 12 bytes) in /home/yoursite/public_html/wp-includes/plugin.php on line 551

In a shared hosting environment the fix is easy.  Add the following to your wp_config.php file:

define(‘WP_MEMORY_LIMIT’, ’64M’);