I have following the problem with my Thinkpad X31 / 2672-c8g /. The laptop don't go to sleep mode after expiry of a sleeptimer. Now I use ACPI driver v.1.55 and Power manager 1.63. I tried also old Battery mixer 1.38. The combination of the keys Fn+F4 works OK. I have OS Windows XPP SP3, 2GB RAM and 250 GB HDD.