What is an ACPI BIOS?
ACPI is an acronym that stands for Advanced Configuration and Power Interface, a power management specification developed by Intel, Microsoft, and Toshiba. ACPI support is built into Windows 98 and later operating systems. ACPI is designed to allow the operating system to control the amount of power provided to each device or peripheral attached to the computer system. This provides much more stable and efficient power management and makes it possible for the operating system to turn off selected devices, such as a monitor or CD-ROM drive, when they are not in use.
ACPI should help eliminate computer lockup on entering power saving or sleep mode. This will allow for improved power management, especially in portable computer systems where reducing power consumption is critical for extending battery life. ACPI also allows for the computer to be turned on and off by external devices, so that the touch of a mouse or the press of a key will "wake up" the computer. This new feature of ACPI, called OnNow, allows a computer to enter a sleep mode that uses very little power.
In addition to providing power management, ACPI also evolves the existing Plug and Play BIOS (PnP BIOS) to make adding and configuring new hardware devices easier. This includes support for legacy non-PnP devices and improved support for combining older devices with ACPI hardware, allowing both to work in a more efficient manner in the same computer system. The end result of this is to make the BIOS more PnP compatible.http://kb.iu.edu/data/ahvl.html
Try disabling power saving features in the control panel such as hibernate and sleep temporarilly until we can determine what is causing this. It may help and cannot hurt.