Continually got this message in WP admin:
'The plugin 0 has been deactivated due to an error: Plugin file does not exist'
Also this from W3 Total Cache:
'One or more plugins have been activated or deactivated, please empty the page cache and check the minify settingds to maintain the desired user experience'
(doesn't matter how many time you clear all caches - both these messages remain)
Trying to change the plugin load order is now no longer successful, and gives this notice:
'The order values were not unique so no changes were made'
The plugin load order does appear to have been changed, but upon refreshing the page, shows no change.
Also now cannot deactivate any plugins (including Plugin Organizer) from WPadmin plugins page.
Rolling back to 3.1.1 (still works OK with WP 3.6)