In order for the examples to work correctly, you need to make sure you have configured the CTR control for your setup. By right-clicking on the CTR control, you can bring up the properties window. Look through the tabs there to make sure that the settings are relevant.
Most importantly, make sure that the Device selected on the general tab is the NI-6601. By default, the Device is just the first device in your computer. This could or could not be the correct hardware, and a mistake here would definately generate a configuration error.