SBS 2003 Event ID 1503 Activesync no unread mails on iphone

[sircles]

I am getting the following in my event log:

Event Type: Error
Event Source: MSExchangeOMA
Event Category: (1000)
Event ID: 1503
Date: 14/04/2011
Time: 13:58:10
User: N/A
Computer: ROLLOVERSRV
Description:
An unknown error occurred while processing the current request:
Message: Input string was not in a correct format.
Source: mscorlib
Stack trace:
at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
at System.Web.Mobile.MobileCapabilities.get_ScreenCharactersWidth()
at Microsoft.Exchange.OMA.UserInterface.MainMenu.OnInit(EventArgs e)
at System.Web.UI.Control.InitRecursive(Control namingContainer)
at System.Web.UI.Control.AddedControl(Control control, Int32 index)
at System.Web.UI.MobileControls.MobilePage.AddedControl(Control control, Int32 index)
at System.Web.UI.ControlCollection.Add(Control child)
at Microsoft.Exchange.OMA.UserInterface.Page.Page_Load(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at System.Web.UI.MobileControls.MobilePage.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain()

Message: Exception of type System.Web.HttpUnhandledException was thrown.
Source: System.Web
Stack trace:
at System.Web.UI.Page.HandleError(Exception e)
at System.Web.UI.Page.ProcessRequestMain()
at System.Web.UI.Page.ProcessRequest()
at System.Web.UI.Page.ProcessRequest(HttpContext context)
at System.Web.CallHandlerExecutionStep.System.Web.HttpApplication+IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)


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No emails are downloaded untilread when they are downloaded no problem.

As far as I know it is only affecting the iphone but may be other handsets also.