When an extension installer is executed, it can fail for various reasons throwing an ExitException. The calling code catches the ExitException and Displays the Launch Error Dialog. If the DownloadWindow is visible, the Launch Error Dialog is parented to the DownloadloadWindows, else it is parented to null.
The problem is the code that launches an extension installer leaves any already visible download window up for five seconds, then removes it.
In many cases the installer has already failed in that 5 seconds, and the LaunchErrorDialog has been created parented to this DownloadWindow. so when the 5 seconds are up, both the downloadWindow and the child LaunchErrorDialog are killed before user can read the error.