Unresponsive 881xp brains

Long post-- short version is "I need help troubleshooting an unresponsive brain-- any ideas are welcome, 'cause all mine aren't working". Installed Python 881xp (= Viper 791xv = Clifford 3.5 etc) in a '97 Accord today. Brain was DOA-- unresponsive to

1. Remote (didn't page back)
2. Valet switch
3. Ignition (didn't lock or unlock doors)

and had both 12V and good ground (.4 ohms back to battery) right at the alarm harness. Unplugged all harnesses, plugged them back in, no luck. Swapped out a new brain, and it worked perfectly first time out-- tach learned, shock sensor, door/trunk/hood pins, etc all worked fine. Both brains are the "old" version-- w/o the extra horn/channel 6 harness. Get home, get the dreaded call from work-- "the Accord is back, and it has the same problem". Multiple installers have checked this alarm, and tried the above stuff (checked 12V & ground @ the main alarm harness, etc). I can't even imagine what could be wrong w/ an install that could actually kill multiple brains, but I've never had a completely dead brain before, let alone two in a row... Just for reference, I'm a fairly experienced installer-- I install 7-10 alarms / RS per week. All connections are   soldered (my background is closer to computers than autos, so I take good soldering seriously) and all connections were tested w/ a digital multimeter prior to being hooked up (in spite of the fact that I've installed in this car easily 10 times in the past year-- and yes, I'm actually that anal). The only non-standard thing I can think of is that I tied two of the outputs (channel 4 & 5) to the cars negative horn trigger (which only took 119 mA to operate). I've done this before, and not had a problem. Aux (channel 2) is connected to the cars negative headlight trigger (something like 2 or 3 mA to operate). Lock and unlock were also well under 200 mA. Parking lights were hooked up to a positive trigger wire, but the fuses are all intact, so I can't imagine that's an issue. Car has no factory alarm... The only thing I can think of is to replace the antenna/shock sensor/XCRS pack in addition to the brain, on the theory that somehow one of them is shorting out the brain. Never seen that, but anything's possible. Please-- any ideas you might have... I have to face this car again tomorrow morning! Me

Try resetting the alarm by unplugging all connections and see if that does the trick.~The Rookie~

Rookie of the year that is...

Don't let the smoke out of your equiptment..it doesn't go back in.

Should have mentioned that above-- the first one was unplugged several times in the process of troubleshooting. I'm not sure about the second one, but I can't imagine that the installer who was troubleshooting it wouldn't have tried that-- he's been around the block a few times. Car didn't come back this morning, so maybe it mysteriously started working again? Yeah, right... Me

Bump..