We have apex classes through which we send emails based on user action in force.com sites. It was working great until Friday, But yesterday when one of our customer try to submit application, they were getting error, In debug it says “SendEmail failed. First exception on row 0; first error: UNKNOWN_EXCEPTION, INVALID_TYPE: sObject type 'SalesforceIqDataSource' is not supported.: []”. I am pretty sure we did not change anything related to apex class, email template, vf page etc.. Does anyone know the reason or best way to fix this?