There are several major issues that M400 owners would like to see addressed. Continual fan usage, mouse lag problems and unstable resume from  standby/hibernation affect many Portege owners. There has been an update that claims to sort out the hibernation problem available  for a couple of weeks. It seems to work OK on my machine.
Toshiba have quietly released a new bios update that DOES NOT claim to fix the outstanding issues but instead a couple of chipset problems.

Of interest is that although the bios update is dated August 22nd, I don’t think that they released it to their site until at least a week later. What gives, Toshiba?

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Download here

Version 1.70 08-22-2006

* Incorporated Intel requirements to optimize chipset memory performance.
* Made a change to support up to the C3-State when “Enhanced C-State” is disabled.

Version 1.60 08-10-2006

* Added support for the Yonah-Celeron CPU.

Version 1.50 06-24-2006

* Added EvDO wireless WAN support.

Version 1.40 05-09-2006

* Corrected an issue where the system could hang when the power supply was turned on during a charge prohibited state of the Peak Shift Function.

Version 1.30 03-29-2006

* Incorporation of Intel’s chipset requirements.
* A change was made to automatically reset the hardware when a restart is performed on Windows XP retail platforms.
* A change was made to reduce power consumption when the Wireless LAN is disabled in Device Manager.
* A change was made to the HD Audio Verb Table for Windows Vista.

Version 1.20 02-08-2006

* Initial production BIOS for Portege M400 models.