Play around with your bios. disable speed step, enable acpi, enable Execute Disable function. There is a post in the HCL where a user says he got your board working.

From: http://wiki.osx86project.org/wiki/index.php/HCL_10.5.2

* Install Method: Kalyway 10.5.2
* BIOS Version: 1201
* Audio: Speaker and Digital Out works (sometimes have some minor issues)
* LAN: OOB
* SATA & IDE: OOB
* JMicron PATA: OOB
* USB: OOB (May not recognize all USB ports)
* Firewire: integrated VIA VT6308 works but crappy... buy a firewire pci card with VT6306
* Had keyboard error with USB/PS2 adapter, no error using PS2 directly
* Install from dvd sata otherwise "still waiting for root device"
* USB DVD Installation works also
* Updating to 10.5.3 using "software update" does NOT work
* Shutdown does not work properly, fans keep rotating