Jaravuy:
Have you reviewed SAP Note 1857710? I had this issue happen at my current client as the MIME files had the extension of ".SWF.BAK" and we needed to remove the ".BAK" so that it ended in ".SWF". Once this was completed, my dashboards showed up. I will mention also that I am using a 7.02 system and not 7.31.
Thanks.
Kevin Tucholke