When your Reporting Services instance is integrated with a SharePoint product or technology and you use Forms authentication, you might encounter the following error when you launch Report Builder:
"Cannot Start Application. Cannot continue. The application is improperly formatted. Contact the vendor for assistance."
To workaround this issue, you must exclude the Report Builder files from requiring authentication by updating the Web.config file and enabling anonymous access.
First, update the Web.config file with the following information so that Report Builder can launch:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <configuration> ... <location path="_vti_bin/ReportBuilder" allowOverride="false"> <system.web> <authorization> <allow users="*" /> </authorization> </system.web> </location> </configuration>
Then enable anonymous access on the ReportBuilder folder in IIS so that Report Builder can connect to the SharePoint Web application.