Error Message: The report parameter ‘P1? is read-only and cannot be modified. (rsReadOnlyReportParameter)
Came across this error last week with any custom report that was uploaded into MSCRM.
The error seems to be a known issue with MSCRM 4 & SSRS 2008 R2
The following workaround should solve this error
To resolve the error message, update the report parameters in the SQL Server Reports Manager to Prompt User for the parameters created by CRM.
1 ) Navigate to the Reports Manager website (i.e. /Reports”>http://<ServerName>/Reports)
2 ) Click to open the <ORGNAME>_MSCRM folder
3 ) Click on Details View
4 ) Click on the 4.0 folder
5 ) Select the Dropdown menu next to the GUID value associated with the report, and select Manage.
6 ) Select Parameters.
7 ) For the P1 Parameter, mark the Hide checkbox
8 ) Repeat Step #7 for all P<#> Parameters that exist and also and CRM_<NAME> Parameters that exist
9 ) Click Apply to save changes
Here is the KB article that will give you more detail on this. http://support.microsoft.com/kb/2410593
** Apparently Rollup 16 Solves this error........so keep updating people! **