WordPress Deactive Plugin

Problem

I had a wordpress site where the public side was fine, but the admin side was throwing a Internal Server Error 500 intermittently.   I couldn’t figure out what was wrong since I had done no changes, and my host said nothing was wrong with the server.  To solve mysterious crashing errors in WordPress, the standard procedure is to first deactivate all your plugins.  However, I could not log in, so how was I to deactivate them?

Solution

A very smart fellow on the wordpress.org forums suggested to log into phpMyAdmin, and look at the wp_options table.  Then look for ‘active_plugins’ string under the option_name field.  Once located, change the option value to  a:0:{}

This deactivates all plugins.  Once deactivated, I re-activated each plugin and found the culprit.  It turned out the plugin was contacting its creator’s server and the creator’s server was down at the time.

source: http://wordpress.org/support/topic/500-internal-server-error-wp-admin-only