The project is ASP.NET 2.0, I have never been able to reproduce this myself, but I get emails informing me it happens to clients many times a week, often a few times in a row.
Here is the full error:
Exception Details:
Microsoft.Reporting.WebForms.AspNetSessionExpiredException: ASP.NET session has expired
Stack Trace:
[AspNetSessionExpiredException: ASP.NET session has expired] at Microsoft.Reporting.WebForms.ReportDataOperation..ctor() at Microsoft.Reporting.WebForms.HttpHandler.GetHandler() at Microsoft.Reporting.WebForms.HttpHandler.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Session Objects:75de8e1d65ff40d1ba666d940af5b118: Microsoft.Reporting.WebForms.ReportHierarchy 5210064be1fa4d6abf5dd5e56b262974: Microsoft.Reporting.WebForms.ReportHierarchy