Lilnux's APM module doesn't work well with a lot of APM bioses out there, strangely it works fine on my Inspiron 4100, do you have the latest BIOS?. For laptops it might be worth looking into 2.6. I've been running 2.6.0-test9 for a while now and havn't had any real problems and the ACPI support is much improved, in 2.4 ACPI wouldn't detect any batteries but 2.6 sees them both correctly.