Hi - yep me again :)
I visited this previously but I dont think I fully understaood the requirements and how to configure but I understand a little more now - but not fully :)
I have created a group on my SQL server (SSMS) and given it the user mapping public & db_datareader permissions to the database and Server Role public.
In the site settings (SSRS) I have created the new group same name as above and given it System User access rights. I have given that group Browser rights on the home folder, and the folder which holds thier reports.
If I log in as a member of that group I can access the SSRS server\report but I get the error
Text
An error has occurred during report processing. (rsProcessingAborted) Query execution failed for dataset 'DataSet1'. (rsErrorExecutingCommand) For more information about this error navigate to the report...