Xbox will not turn off.

My xbox will not turn off using the power button - I have to unplug it. When I plug it back in, the power is already on. The light is a constant green and everything else seems to be working properly. How can I fix this?

 

try taking off the faceplate, might be the button's become jammed.

 

I replaced the face. The funny part is that i can turn it off with the menu but can't turn it on unless i dissconnect it from the wall. then ti turns on by it self... oh and it plays normal...

 

well how old is it? perhaps you could get a replacement on warranty, if its within a year from purchase.

 

Well its the first model. and its modded.....

 

Kind of sounds slightly untechnical but have you tried just prodding the power button with a biro or something when the faceplate's off.
It sounds to me as though the buttons jammed in.

 

This problem has been around for years

 

http://forums.llamma.com/viewtopic.php?t=12329&highlight=trace+corrosion
might be trace corrosion........
i too had, some time ago, a first model xbox with the same problem that you had. the power on/of didn't respond, i my case i had trace corrosion (after some time it also started to randomly shut down after a few hours of gameplay). i had to retrace a few traces, after which the problem was solved (and the power on/of button again worked). same as c4rn1 replied btw....