Dell N4050 doesnot shutdown completely

[arun48]

When i click shutdown or hibernate it does so but doesnot power off completely
i.e. fan keeps running and power led glows with no response to any keys
to turn off i have to press power button for 2-3 secs.
but reboot works fine
When i first got hands on it it worked fine .
i am using windows 7-64 bit
this error also occurs with linus OSes (ubuntu 10.10, backtrack4r1,slitaz)

please help what could be the problem

 

[pranav0091]

Looks like a faulty motherboard to me. My friend had a toshiba which would not go to sleep, we initially though it was an OS or driver issue, which is what the tech support also claimed. but then much later in a totally unrelated case, got the motherboard changed and the issue disappears. this one looks similar. I hope the laptop is under warranty.