Update: On the 17th of October 2012 Microsoft released Rollup 11 (with a re-release of the outlook client) which addresses this issue. You can download it from the link below. http://www.microsoft.com/en-us/download/details.aspx?id=34969
In August rollup 10 was released for Dynamics CRM 2011, this had a number of breaking changes, here are few of them:
• Issues with saved queriesAbout a week ago version 2 of rollup 10 was released, this unfortunately has another side effect. If you configure Claims/IFD and you have old CRM 4 plugins that were upgraded to CRM 2011 they will stop working with the above “The request failed with HTTP status 404: Not found” error. In the event viewer you’ll see a similar error to the one below:
The Web Service plug-in failed in OrganizationId: 010c9151-dbf0-4695-af40-96bcc0fa09f6; SdkMessageProcessingStepId: ad5c7b04-1b4c-4e74-a88b-855302de3b39; EntityName: account; Stage: 50; MessageName: Update; AssemblyName: CRM4.Plugin, CRM4.Plugin, Version=6.3.0.0, Culture=neutral, PublicKeyToken=e86f6c07b0fe8025; ClassName: CRM4.Plugin; Exception: Unhandled Exception: System.Net.WebException: The request failed with HTTP status 404: Not Found.
at Microsoft.Crm.Extensibility.LegacySdkTypeProxyMetadataServiceWrapper.InternalInvoke(MethodInfo methodInfo, Object[] parameters)
at CRM4.Plugin.Execute(IPluginExecutionContext context)
at Microsoft.Crm.Extensibility.V4PluginProxyStep.ExecuteInternal(PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
There are couple of ways around this issue.