Fatal error creating nodes with emfields

I've used the emfield module to create a node type called "Video", which contains a video field (among other things).

When the user creates a video node, workflow-ng creates a corresponding Drigg node, with the same Title, referencing the Video node... or at least, that's what's supposed to happen.

What happens instead is that in its attempt to generate the Drigg node, Drupal throws this error:

"Fatal error: Only variables can be passed by reference in /www/110mb.com/s/a/t/o/r/i/_/_/satori/htdocs/Drupal/modules/emfield-5.x-1.2/emfield/contrib/emthumb/emthumb.module on line 155"

...and creates a corresponding Drigg node with the appropriate title, but which doesn't reference the Video node. Taxonomy terms are shared between Video and Drigg node types, but aren't passed - this may be due to the fatal error halting the node creation mid-process.

Workflow-ng seems to be trying to pass the field information from emfield in its creation process (to a Drigg node which knows not what to do with it), but I'm not proficient enough to know for sure that this is the case.