Comment 9 for bug 545508

I can reproduce this on a Lenovo Thinkpad x100e

Disconnecting the AC Power freezes the system.
Booting on battery power works until the login screen, then freezes as well.
Setting acpi=off at boot time didn't work the first time I tried a few days ago but i will retest that.

Toggling display brightness via hotkeys or power manager freezes the system as well, but i think that has something to do with thinkpad_acpi not yet supporting the x100e model ("not yet supported thinkpad detected")
http://sourceforge.net/mailarchive/forum.php?thread_name=20100316230950.GA30415%40khazad-dum.debian.net&forum_name=ibm-acpi-devel