[Plugin: Formstack Online Forms] Formstack Worpress Plugin Error

I get the following error in using the Formstack plugin on my website:

Warning: file_get_contents() [function.file-get-contents]: URL file-access is disabled in the server configuration in /homepages/40/d159821754/htdocs/toxic-injury/blog/wp-content/plugins/formstack/Widget.php on line 46

Warning: file_get_contents(http://www.formstack.com/forms/wp-ad.php?form=1004952) [function.file-get-contents]: failed to open stream: no suitable wrapper could be found in /homepages/40/d159821754/htdocs/toxic-injury/blog/wp-content/plugins/formstack/Widget.php on line 46

You can see live on my website at: http://www.toxicinjurylawyer.com/blog/toxic-exposure/

How can I resolve this problem? Is there a modification to the code I can make at line 46?