System.InvalidOperationExceptionOperation is not valid due to the current state of the object.
System.InvalidOperationException: Operation is not valid due to the current state of the object.
at Rhino.Commons.LongConversationManager.LoadConversationFromRequest(Boolean& privateConversation)
at Rhino.Commons.HttpModules.UnitOfWorkApplication.UnitOfWorkApplication_BeginRequest(Object sender, EventArgs e)
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
Microsoft recently (12-29-2011) released an update to address several serious security vulnerabilities in the .NET Framework. MS11-100 was introduced just recently that handles potential DoS attacks.
Unfortunately the fix has also broken page POSTs with very large amounts of posted data (form fields). MS11-100 places a limit of 500 on postback items. The new default max introduced by the recent security update is 1000.
Adding the setting key to the web-config file overcomes this limitation, as in this example increases it to 2000.<appSettings>
<add key="aspnet:MaxHttpCollectionKeys" value="2000" />