Strange. I just installed mine a couple weeks ago and no problems. I don't know if this helps, but Sean at HF advised me to leave my driver side door open. Here are his words:
"NOTE : When tuning, leave the driver side door open so the key off steps and completely turns off everything."
Do you need to flash your PCM??? More notes from Sean:
"When you get the tuner, first thing is to plug it up to your pc and run an update using dsdownloader which you can get from the Diablo website. That's found in the downloads section on the Diablo site. Run dsdownloader with the trinity attached to ur pc. Then click on the express tab and then click on update tool. Then load a preloaded tune file in ur vehicle. If your pcm isn't at the latest flash revision it will state that and then you can go back to ur pc and run dsdownloader. Click on Calibration Update to download your new pcm info into the tuner. Once completed carry it back to the vehicle and it will flash the pcm with the latest revision. If you have any trouble with that, contact DiabloSport tech support and they can walk you through it. Once that is done, THEN you can load in a preloaded tune file."