Got a message on the plugin page that it didn't work and had been deactivated. Checked my site. Sure enough, everything was messed up. Reverted back to an older version, site works. Probably should have copied the error message that was at the top of every page on my site, but I didn't. Sorry. Something about a callback to featured...something. Something about line 405 in plugins.php
Don't know if that helps.