That sounds to me its a problem with your ACPI (Advanced configuration and Power interface).
I've a Acer Aspire 1692 WMLi DDR2 and i had that similar problem.
The problem is that some laptops (because of the manufacturers) came with ACPIs that only work well in windows.
To solve that problem you'll have to insert a fixed DSDT (Differentiated System Description Table) in the kernel at boot time.
If you dont do this, your laptop will still working, but you'll not be able to use the power funcions to save laptop battery...
go to acpi.sourceforge.net
and see if for your bios there is a fixed DSDT that you could use. If exists, check the documentation to see how to insert the fixed DSDT in the kernel...
If you cannot find a fixed DSDT, or you wait for someone to fixed a DSDT for your laptop,
or you could fixe it yourself.
REMEMBER: the DSDT is bios dependable, that means if you upgrade your bios and you have a fixed DSDT, you'll have to fix the DSDT again
the site is well documented and theres a lot of information in the internet about that...