Enterprise Vault OWA extensions with event ID 0.

Hi Guys,

Just updated the EV server from 2007 to 8. We have started getting error messages in Event log on HUB/CAS servers:

Level: Error
Source: Enterprise Vault OWA extensions
Event ID: 0

System.NullReferenceException: Object reference not set to an instance of an object.
   at Symantec.EnterpriseVault.Owa.Core.EVContext.GetOWASessionId(HttpContext oHttpContext)
   at Symantec.EnterpriseVault.Owa.Core.EVContext.GetEVContext(HttpContext oHttpContext, SecurityIdentifier sid)
   at Symantec.EnterpriseVault.Owa.Core.RequestProcessor..ctor(HttpContext oContext)
   at Symantec.EnterpriseVault.Owa.EVOwaModule.PreRequestHandlerExecute(Object objSender, EventArgs objEventArgs)"
Error,30.03.2009 08:38:21,Enterprise Vault OWA Extensions,0,None,"An unhandled exception was caught in PostRequestHandlerExecute:
   Page: /owa/default.aspx?ae=Folder&t=IPF.Note&a=
   User: INTERNAL\D870042
   HTTP Request Timestamp: 30-03-2009 08:38:21

Anyone seen this before? All help will be very appriciated. Thanks