I used my multimeter and the opus is getting a constant 13.86-13.88 Volts, and we already booted it up with the minimal amount of hardware connected.
Try to go for minimal configuration and see how stable it runs. Disconnect the HDD, CDROM and other stuff you dont need...just boot up the motherboard as bare as possible.
If all is well connect your HDD and see how it goes.
Im suspecting the OPUS is having problem supplying enough current to all your devices. Probably the reason why it reboot after few seconds because the devices start getting switched on by the motherboard.
The possible problems are :
Your battery is not supplying enough to OPUS.
Bad connection to the OPUS and battery.
You are overloading the OPUS.
can I re-suggest that you try it indoors on a car battery with the opus, or get 110vac to 12V supply and try it indoors again with the opus.
also check that the ACC supply that you are using from the ignition is supply a constant 12V and isn't fluctuating.
Also check your connections to make sure something isn't shorting to ground.
Thanks for all the suggestions and what not.
Last night I finally got our car computer to run and stay powered on longer than 5 seconds. We called Kris at Opus Solutions and he recommended we get a motherboard that had the 12V connector on it. So we got in the new board, installed it and made a new ground. We are not sure if it was the new mobo or the better ground that made the difference, although personally i think It kept rebooting in the truck due to a poor ground.
Either way the problem has been resolved and everything seems to running fine for now. Thanks for all the suggestions and advice.