ubuntu reboot upon monitor disconnect--why?

Question

I have a brand new computer, running Kubuntu 9.04. If I unplug the VGA monitor, the system reboots. I have never seen this before. I am prepared to believe it is some weird hardware problem, and I have contacted the vendor for help, but their Linux guy is away (the lucky guy has been at the Olympics)--they swear they extensively tested before shipping, and want to defer the answer until he gets back.

My question is whether anybody knows of any setting in Linux that could cause this. It seems to me it must be hardware related. I have tried several monitors, etc, it happens on all of them--it does not happen when I power off the monitor instead of disconnecting it.

Answer 1

Almost certainly an electrical problem - probably a short if the earthed doesn't connect first.

Probably not a good idea to do this!

Answer 2

Perhaps try a different distro / kernel with a LiveCD and see if that changes anything?

Answer 3

In the usual way that this happens, I found my issue within minutes of posting a question on Stack Overflow (By the way, my apologies for posting in the wrong place first). I was troubleshooting for a couple of hours, calling the vendor, etc before asking for help--then once I asked, I discovered the "solution"--not the cause, that still mystifies me.

Anyway, There is an in-line DC connector between the power supply and the computer. It was backed off a little. When I make a completely firm connection, the problem never happens.

Remember, it is connecting and reconnecting the VGA connector that makes the machine reboot. It is physically nowhere near the power connectors. I still have no idea why a VGA reconnect will cause a machine to reboot--it's not that the connection is poor and can't substain a surge or anything like that, because there is no problem in booting from power up, and it makes no difference if the monitor is turned off when I reconnect.