You are right @passimal.
With JM Twitt Cards 5.2.8 the problem is solved.
Thanks everydoby.
What I do to use NextGen Gallery is to deactivate JM Twitt Cards, and then I can use NextGen Gallery. When I have finished I activate JM Twitt Cards agains. I know that this is not your fault. I am sure this JM Twitt Cards’ fault.
I have the same problem: Fatal error: Class ‘JM_TC_Tabs’ not found in /web/htdocs/www.barriodelpilar.com/home/wp-content/plugins/jm-twitter-cards/jm-twitter-cards.php on line 205
