1.9A is too close to the 2A capability of supply power. Your arduino needs power as well as the TLC5940s to run. You may be dropping voltage down too much with a struggling VR. Is it getting hot? If so, do you have heat sinks on it? Have you measured the measured the max current of the entire circuit? Are the fans drawing power from the 5V 2A power as well? What is the rating of the 12V source you mentioned?
Where is the "5V and 2A" for the LEDs supplied from?
5v 2A is powering just the 20 RGB led's across the anodes. (60 Led's running at 20mA each)My arduino is powered by 12v into the Vin. The rating of the 12v source is 5A and 60W. (Also powering my fans)the second 5v power supply is from the arduino's 5v. This is for the Tlc5940's.