I disabled logging from the System > Advanced > Developer screen (I've checked that is disabled for all the websites/stores/storeviews) but Magento continues to write errors inside "/var/log/system.log" like:
[...] ERR (3): Warning: simplexml_load_string(): [...] in /lib/Varien/Simplexml/Config.php on line 383
Are there errors that ignore the admin backend setting?