Upgraded WP to 3,9, Atahualpa to 3.7.15, NextGEN gallery to 2.0.61 --> fatal error

I got this fatal error below (exact file location varies) on trying to login to admin area starting Saturday for no apparent reason.
I have removed all unnecessary plugins and updated everything. NextGEN gallery now works fine and there is no error when I activate it in a default theme but when I activate in either the new version of Atahualpa or my previous version (was 3.7.12) it throws the same error and I can't access admin area. The visible front end works fine whether nextgen is enabled or not.

website is http://decosmos.org

"Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 122880 bytes) in /home/decos216/public_html/decosmos.org/art/wp-admin/includes/class-wp-plugins-list-table.php on line 148

The Php info access on server is http://decosmos.org/phpinfo.php and shows memory limit 128M

Incidentally the atahualpa upgrade removed the widgets from both 'inner' sidebars and moved them to 'inactive sidebars' at the bottom of the widgets screen. I had to move them back to the correct sidebars.