We seem to have picked up a latent issue in the VS 2010 ReportViewer Webforms control (v10) when the NLB cluster affinity setting on our IIS 6 web server was changed from "Single" affinity to "None.
It seems that when the RV control renders using Ajax, that the Server assumes that the browser control will return to the same server during rendering (which will not necessarily be the case with NLB without affinity). (also it is apparant that the RV control uses another state tracking mechanism other than Session State - we use SQL Session state on the application in which the Control is used).
(The application has been in a production environment for 2 years without this issue. And the issue doesn't occur if a) we re-enable affinity on the NLB cluster or b) Instruct users to directly access one of the indivdual servers in the NLB)
Applicable settings on the control are
ProcessingMode = Microsoft.Reporting.WebForms.ProcessingMode.Remote;
AsyncRendering = true;
We also use SQL Session state.
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; SLCC1; .NET CLR 2.0.50727; .NET CLR 1.1.4322; .NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618; MS-RTC LM 8; InfoPath.3; .NET4.0C; .NET4.0E)
Timestamp: Fri, 30 Mar 2012 09:29:32 UTC
Message: Sys.InvalidOperationException: Type Sys.UI._Timer has already been registered. The type may be defined multiple times or the script file that defines it may have already been loaded. A possible cause is a change of settings during a partial update.
Message: Sys.ScriptLoadFailedException: The script '/myApp/ScriptResource.axd?d=zIwq3H9TfZpVP2jrtOYLZJK7knZ4dYRnF8jieeZ0WV6cAW_sAVjbLL-M_mFO20YL6UeRpXRFCXWAe1PawNn6r7TxmEjGZLUys1lrcICU4G7UFj8ZnRV9HNNYMGuh7XZMyv48_0ZYA1VJy7Qf7kIAFRu3stao2NUiByAw20xTrbMhHDok0&t=14af6a58' failed to load. Check for:
Script errors. (IE) Enable 'Display a notification about every script error' under advanced settings.
Missing call to Sys.Application.notifyScriptLoaded().