Hi all,  
  
Whenever i try to browse the OMA siteo on IE, i will get ": A System error  
  
has occurred while processing your request. Please try again. If the problem  
  
persists, contact your administrator." error. On the event log, the above  
  
event ID is logged. This is the details in the event log:  
  
An unknown error occurred while processing the current request:  
  
Message: Object reference not set to an instance of an object.  
  
Source: Microsoft.Exchange.OMA.Preferencing  
  
Stack trace:  
  
at  
  
Microsoft.Exchange.OMA.Preferencing.AdUserObject.FindUserViaCreds(NetworkCredential creds, WindowsIdentity identity)  
  
at Microsoft.Exchange.OMA.Preferencing.OmaUserInfo.ClearCache()  
  
at  
  
Microsoft.Exchange.OMA.Preferencing.OmaUserInfo..ctor(NetworkCredential  
  
creds, WindowsIdentity identity)  
  
at  
  
Microsoft.Exchange.OMA.Preferencing.OmaUserInfo..ctor(NetworkCredential creds)  
  
Message: Exception has been thrown by the target of an invocation.  
  
Source: mscorlib  
  
Stack trace:  
  
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(BindingFlags  
  
invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean  
  
isBinderDefault)  
  
at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags  
  
invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)  
  
at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder  
  
binder, Object[] args, CultureInfo culture, Object[] activationAttributes)  
  
at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr,  
  
Binder binder, Object[] args, CultureInfo culture, Object[]  
  
activationAttributes)  
  
at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object  
  
sender, EventArgs e)  
  
Message: Exception of type  
  
Microsoft.Exchange.OMA.DataProviderInterface.ProviderException was thrown.  
  
EventMessage:  
  
UserMessage: A System error has occurred while processing your request.  
  
Please try again. If the problem persists, contact your administrator.  
  
Source: Microsoft.Exchange.OMA.UserInterface  
  
Stack trace:  
  
at Microsoft.Exchange.OMA.UserInterface.Global.Session_Start(Object  
  
sender, EventArgs e)  
  
at System.Web.SessionState.SessionStateModule.CompleteAcquireState()  
  
at System.Web.SessionState.SessionStateModule.BeginAcquireState(Object  
  
source, EventArgs e, AsyncCallback cb, Object extraData)  
  
at  
  
System.Web.AsyncEventExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute()  
  
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&  
  
completedSynchronously)  
  
Pls advise how can i troubleshoot such errors.