After switching host locations for my wordpress blog at the weekend I found I could not access my website due to errors in various plugins. After renaming the offending plugins’ folders on the server my page was functioning again, but when I attempted to login as admin to reactivate the plugins I was greeted by a 500 error.
After Googling I discovered the following solution was to deactivate all plugins in the database to regain access to the administrative menus.
Find the active_plugins row in the wp_options table,
Change the value of the field to: a:0:{}