cavorite, you have two choices - listen for people and do what they recommend or stop writing here and do whatever you want
1. Terminal program status indicator doesn't show HARDWARE status - it just shows logical state your OS port, not usb2ttl in your case.
2. You have to disconnect your usb2ttl from DX and connect RX to TX wire of usb2ttl together. This way you will test HARDWARE of your usb2ttl - if TX sends AND RX receives data. If you will see echo - it means that TX sends ELECTRICAL signal and RX is able to receive it and send back to USB. I suspect that you burned your usb2ttl RX port (or both TX/RX). If you will see the echo - it means that usb2ttl is OK and you burned your DX serial port (at least TX) or something wrong with your uboot (low chance).
I'm not very familiar with uboot internals but looking at environment variables I think it's possible to set uboot wrong way so it will configure serial interface for wrong speed/port.
Originally Posted by cavorite
@equinox1 - everything was working with no problem a few days ago. Nothing has really changed other than whatever is happening inside the DX softwarewise. I've verified that the driver is present and my comm programs are seeing and connecting to it as a serial port. One program, coolterm, goes as far as to have led-like status indicators for tx, rx, cts, dtr, etc., and I can see activity on the TX line when I type on the keyboard, but no activity on RX, i.e. no character echo back from the DX.