To fix error below:
PHP Warning: Unknown: Unable to allocate memory for pool. in Unknown on line 0
You should increase APC opcode cache parameter apc.shm_size, which is set to 32M by default and restart web server Apache module if PHP is set to wokr like web server module.
One more thing, you can switch off APC module for some domain or virtual host you can add the following lines to your .htaccess configuration file:
<IfModule mod_php5.c> php_flag apc.cache_by_default off </IfModule>
