We have been using a scenario described here: http://xrmmatrix.blogspot.in/2011/06/creating-report-as-pdf-attachment-in.html for creating reports as a pdf attachment from CRM 2011 and it worked fine so far.
After applying the SP1 update (or "Spring wave" on CRM Online), it stopped to work. The report server returns a text file with "pdf" extension and the error message inside. Something must have changed.