Thanks for the quick reply.
I checked as you suggested: the server settings looked slightly different because I had an older version of the plugin (1.5.5) on the other site. I auto-updated it to 1.6.2, which made the server settings identical for both sites. Then I tried to use NextGen on the other site and got the same error msg: “Fatal error: Only variables can be passed by reference in /home/mattsoar/www.mattsoar.org/wp-content/plugins/nextgen-gallery/lib/meta.php on line 385”.
Happy to try other fixes. I am not a programmer, but I checked line 385 in the file meta.php and it says on the line before:
//TODO:Review this, reports sometimes a error “Fatal error: Only variables can be passed by reference” (PHP 5.2.6)
Best wishes,
Matt