Serial communication failure when using power supply

Will try the capacitor trick for the reset, i heard the resister doesn't work on uno r3. Could very well be a reset problem. I am now testing an unregulated 7.4v supply (puts out 10.3v under arduino load), and so far no resets, but it hasn't been a long time yet. I don't think it's my machine since I've had the terminal open for hours normally without any issues.