Make sure you are running the latest version of Color Finesse, version 3.0.14. We fixed a problem that is similar to your description.
If that doesn't fix things, we'll need more information such as PC or Mac, operating system version, description of your hardware, and whether it hangs every time you launch the UI. Also, are you applying Color Finesse to a footage layer or adjustment layer.
You can download the 3.0.14 installer from our website.