Adding update() to that method works perfectly!
With that edit, setting the text first then ResetToBeginning() works exactly as intended:
TextLabel.text = "Hello World";
TypeWriterComp.ResetToBeginning();
If you could, it would be great if you could add that to it in the next NGUI update so it doesn't have to be fixed manually each update.
Thank you very much, ArenMook!