PHP Warning in my error_log

I keep getting this in my error_log. Everything seems to be working OK as far as viewing my site. When i disable all plugins and then activate one by one, NextGen seems to be causing this error. I”m using PageLines theme. My website is:

text/x-generic error_log
ASCII C++ program text
[10-Oct-2013 18:48:50] PHP Warning:  call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in /home/denisep9/public_html/wp-includes/plugin.php on line 406

http://wordpress.org/plugins/nextgen-gallery/