MultiError is a small, command-line utility (à la ResFind) which you can call to generate a multi-tasking error or message window. It is intended to be used in your !Run files, but there's nothing to stop you using it from within your actual program to launch independent message windows. Apart from the multi-taskingness, it also provides an extra button which users can click on to visit a website and it logs the error message using SysLog. (These two "extras" are only implemented if relevant and possible on the user's system.)