When I executed reports in CRM 2011 by selecting more than 20 records it give the following error:
Microsoft.Reporting.WebForms.ReportServerException: An error has occurred during report processing. (rsProcessingAborted) ---> Microsoft.Reporting.WebForms.ReportServerException: Query execution failed for dataset 'DsPhoneCallBase'. (rsErrorExecutingCommand)
This is happening for both system reports and custom reports.
When you review the SSRS log you might find this error.
The SELECT permission was denied on the object ‘fn_GetGuidsFromString’, database ‘MicrosoftCRM_MSCRM’, schema ‘dbo’.
If so then this is a known issue supposedly fixed in UR8. You will find reference to it here http://blogs.msdn.com/b/crminthefield/archive/2012/04/20/podcast-and-overview-microsoft-dynamics-crm-2011-update-rollup-8.aspx
See this blog for a work around until you upgrade.
If possible, attach a SQL Server Profiler to the database server and make sure to include "Events: Error" in the events selection. This will show you which statement fails and why.
You might also be able to find pointer in the reporting services log files:
%ProgramFiles%\Microsoft SQL Server\MSSQL.x\Reporting Services\LogFiles
