Warning error messages -- two regarding file_get_contents function (embedded video/thumb)

I just finally upgraded this module (and ran update.php), and I went to review and edit my settings for an existing embedded-video content field, and then things went icky. I am seeing these two warning messages:
warning: file_get_contents() [function.file-get-contents]: URL file-access is disabled in the server configuration in [...]sites/all/modules/emfield/contrib/emthumb/emthumb.module on line 557.
warning: file_get_contents(http://img.youtube.com/[...].jpg) [function.file-get-contents]: failed to open stream: no suitable wrapper could be found in [...]sites/all/modules/emfield/contrib/emthumb/emthumb.module on line 557.
I did change the settings for the custom thumbnail image -- then I changed them back after getting the warnings. But the messages are still appearing every time I go into the node-edit form (for the node with this content field) and intermittently when I just view the node. (So I re-changed the setting for storing-remote-thumbnail-images locally to "don't do this," since reverting the change didn't help.)

(I'm using a custom thumbnail image.)

A weird thing about this is that the custom thumbnail image appears to be displaying just fine. But... the error...

Any thoughts? Thank you!