[kwlug disc.] acpi / apm laptop hardware issue

[Richard Weait]

I've been asked to take care of a problem with an older laptop.  It's
a Dell Inspiron 1100 running Ubuntu 7.04 and the backlight does not
switch off with the lid closes.

I'm not familiar with running around poking at hardware issues.  So
I've hit a few google things and randomly smashed the keyboard.
Oddly, the symptoms still exist.

dmesg claims that ACPI is okay
ACPI: Interpreter enabled
and that the lid switch is found
ACPI: Lid Switch [LID]

lshal -m is told to monitor device states, but does not see the lid
switch activate.  It does see things like the AC connector
disconnecting.  Backlight brightness changes from the keyboard show up
here nicely.

acpitool -e lists lots of acpi stuff including
LID        3         * ENABLED

What should I try / check next, without resorting to a hammer?