Error when load


I try to use the SilverlightInput.dll in a SL3 project with the following deckaration:
<inputdata:MaskedEdit x:Name="maskEdit" Grid.Row="4" Grid.Column="1" Mask="999.99"/>
When the application start the following error raises:
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; InfoPath.2)
Timestamp: Wed, 19 May 2010 13:13:59 UTC
Message: Unhandled Error in Silverlight Application
Code: 4004
Category: ManagedRuntimeError
Message: System.Exception: Property Mask is invalid
at Silverlight.InputCtrl.MaskedEdit.MaskEdit_Loaded(Object sender, RoutedEventArgs e)
at System.Windows.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, String eventName)
Line: 56
Char: 13
Code: 0
URI: http://localhost:2835/DataBindingTestPage.aspx