There are few things you can do:
a) Look at the attached VI. When you want to open a VI that runs when open, this VI will open it idle mode using VI Server.A nice touch to improve your LabVIEW environnement, copy that VI in the labview\wizard directory. After relaunching LabVIEW, a new item will appear in the file menu: Open VI idle mode. That makes the VI easily accessible when needed.
b) On the diagram of a new VI, drop the problem VI. Clicking the VI icon on the diagram to open its panel, this one won't be running.
c) In case of emergency, put a VI (or a shortcut to) on the desktop that will abort all top level VIs currently running (except itself). When the user interface is stuck with a modal VI that prevents all other user operation, double-cl
ick on this VI to abort. That prevents to have to kill LabVIEW.