I have the same problem on an emachines 370 desktop. The CPU fan never appears to come on and it overheats when doing intensive work (Last time, in the middle of regenerating an initramfs during an upgrade!). The fan works fine in Windows XP, and worked under previous versions of Ubuntu (I think Hoary - but not too sure). Coincidentally ACPI reports bogus temperatures for the CPU
~$ cat /proc/acpi/thermal_zone/THRM/temperature
temperature: -267 C
~$ acpi -t
Thermal 1: passive , 4294967040.0 degrees C
I've also added this to bug 54554 since it seems similar [If not a dupe]
I have the same problem on an emachines 370 desktop. The CPU fan never appears to come on and it overheats when doing intensive work (Last time, in the middle of regenerating an initramfs during an upgrade!). The fan works fine in Windows XP, and worked under previous versions of Ubuntu (I think Hoary - but not too sure). Coincidentally ACPI reports bogus temperatures for the CPU
~$ cat /proc/acpi/ thermal_ zone/THRM/ temperature
temperature: -267 C
~$ acpi -t
Thermal 1: passive , 4294967040.0 degrees C
I've also added this to bug 54554 since it seems similar [If not a dupe]