openecu.org

I have the single ground tactrix cable for Evos that I bought about 5 months ago. I only flashed the car a couple times, and now it doesn't work.

I plug it into my Evo, and when I hit read ecu, EcuFlash doesn't do anything, then when I click it again, it crashes. Nothing has changed, previously it was working just fine.

What do I do with it? Is it something I can fix?

I've heard of a few failures with these. If you're feeling brave, download the schematic from this site and see if you can find the dead parts. The case is glued together but not too hard to disassemble.
The most likely failure point with the EVO cable is the VPP generator circuit (charge pump that generates 17-18V for putting ECU in boot mode).

how does the circuit typically fail? does it develop an open? Is it something I can remove and soder back on? I looked at the schematic and from what I can tell vppEN starts at CBUS2 which is FT232RQ. Do I cut that out? or maybe it's the switch that's bad. How do I send power to it to test it? Just plug it into the car?

The most likely thing to fail are the transistors that are directly visible to the 'real world', i.e., connected directly to the OBDII connector pins. The VPP circuit generates 18V all the time IIRC; check that, then if it's good, check the switch.
All those parts are easy to get and can be unsoldered/resoldered.

Thanks a lot for the help. Much appreciated.