the stack trace displays my method's name then "external code" then app_unhandledexception method, I'm developing within VS2008 SP1 for silverlight on firefox and windows 7(if that makes a difference). the weird thing is, the updatelayout method is called elsewhere and it generates no exception there, that said, if I put the method within a try-catch clause, it doesn't catch the exception, so if anyone has an idea, I'd appreciate it.