在启动屏幕关闭后将主窗口置于前面

I have run into a problem with a custom wpf splash-screen implementation. The problem is that after the loading is finished and the MainWindow should be shown, it sometimes is not brought to front i.e Activate() call fails. It happens maybe 1/10 times. Application is run on Windows7/64.I have run into a problem with a custom wpf spl