if i could interject something.  BIOS updatat A08 modified some of the acpi thermal zones for the L400 and might lead to issues of over heating for Linux (actually this issue can be seen with Windows 2000 also).  I have found that rolling back to BIOS A06 brought ACPI back for Linux.  I'll attatch the a tarred /proc/acpi from Xubuntu 7.04 running the A06 BIOS for possible comparision.

[    0.000000] ACPI: BOOT (v001 PTLTD  $SBFTBL$ 0x20010709  LTP 0x00000001) @ 0x0ffffbd9
[    0.000000] ACPI: DSDT (v001    PTL    BX-TJ 0x20010709 MSFT 0x01000007) @ 0x00000000
[    0.000000] ACPI: PM-Timer IO Port: 0x8008
[   10.616886] ACPI: Core revision 20060707
[   10.618760] ACPI: Looking for DSDT in initramfs... file /DSDT.aml not found, using machine DSDT.
[   10.623205] ACPI: setting ELCR to 0200 (from 0c00)
[   10.631384] ACPI: bus type pci registered
[   10.649941] ACPI: Interpreter enabled
[   10.649954] ACPI: Using PIC for interrupt routing
[   10.650862] ACPI: PCI Root Bridge [PCI0] (0000:00)
[   10.651698] PCI quirk: region 8000-803f claimed by PIIX4 ACPI
[   10.652220] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
[   10.654566] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0.AGP_._PRT]
[   10.655385] ACPI: PCI Interrupt Link [LNKA] (IRQs 3 4 5 6 7 9 *10 11 14 15)
[   10.656130] ACPI: PCI Interrupt Link [LNKB] (IRQs 3 4 5 6 7 9 *10 11 14 15)
[   10.656706] ACPI: PCI Interrupt Link [LNKC] (IRQs 3 4 5 6 7 9 10 11 14 15) *0, disabled.
[   10.657309] ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 6 7 9 10 *11 14 15)
[   10.700500] ACPI: Device [FDDA] status [00000008]: functional but not present; setting present
[   10.703142] ACPI: Device [CDRM] status [00000008]: functional but not present; setting present
[   10.709888] ACPI: Power Resource [PFN0] (off)
[   10.710196] ACPI: Power Resource [PFN1] (off)
[   10.710363] pnp: PnP ACPI init
[   10.788292] pnp: PnP ACPI: found 12 devices
[   10.788308] PnPBIOS: Disabled by ACPI PNP
[   10.788467] PCI: Using ACPI for IRQ routing
[   10.792240] ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
[   10.792257] ACPI: PCI Interrupt 0000:00:0a.0[A] -> Link [LNKA] -> GSI 10 (level, low) -> IRQ 10
[   12.992957] ACPI: (supports S0 S3 S4 S5)
[   15.679079] ACPI: Transitioning device [FAN0] to D3
[   15.679089] ACPI: Transitioning device [FAN0] to D3
[   15.679100] ACPI: Fan [FAN0] (off)
[   15.679241] ACPI: Transitioning device [FAN1] to D3
[   15.679248] ACPI: Transitioning device [FAN1] to D3
[   15.679256] ACPI: Fan [FAN1] (off)
[   15.692135] ACPI: CPU0 (power states: C1[C1] C2[C2])
[   15.692151] ACPI: Processor [CPU0] (supports 8 throttling states)
[   15.700460] ACPI: Thermal Zone [THRM] (50 C)
[   11.064000] ACPI: PCI Interrupt Link [LNKD] enabled at IRQ 11
[   11.064000] ACPI: PCI Interrupt 0000:00:07.2[D] -> Link [LNKD] -> GSI 11 (level, low) -> IRQ 11
[   11.172000] ACPI: PCI Interrupt 0000:00:0d.0[A] -> Link [LNKA] -> GSI 10 (level, low) -> IRQ 10
[   31.044000] ACPI: PCI Interrupt Link [LNKB] enabled at IRQ 10
[   31.044000] ACPI: PCI Interrupt 0000:00:08.0[A] -> Link [LNKB] -> GSI 10 (level, low) -> IRQ 10
[   32.384000] ACPI: PCI Interrupt 0000:02:00.0[A] -> Link [LNKA] -> GSI 10 (level, low) -> IRQ 10
[   37.548000] ACPI: Battery Slot [BAT1] (battery present)
[   37.600000] ACPI: AC Adapter [ACAD] (on-line)