"Serialization of 'SimpleXMLElement' is not allowed."

Hi, I am using Feeds 6.x-1.0-beta13 and recently, I have not been able to import new items from an rss feed, and am given the error message "Serialization of 'SimpleXMLElement' is not allowed." I don't really know how to fix this, so could somebody please tell me what to edit in my feeds module in order for this to function properly? Thank you so much.