I'm using the same RAM module as you are, and the Mobo is ABiT iX38. Honestly I have the same problem with you, I was unable to change the setting to 4-4-4-12 on the BIOS. However I found this setting at corsair forum:
Motherboard make and model: Asus P5WD2 or M2N32-SLI Premium/Deluxe
Each pair is tested and packaged together using the following settings:
AI Over Clock Tuner: Manual
CPU External Frequency: Manually set to 200MHz
DDR2 SDRAM Clock: Manually set to 800MHz
PCI Express Freq: Auto
PCI Freq: 33.33
Performance Mode: Standard
DRAM Timing Selectable: Manual
SDRAM CAS Latency: 4T
SDRAM RAS to CAS Delay (tRCD): 4T
SDRAM Row Precharge (tRP): 4T
SDRAM Active to Precharge Delay (tRAS): 12T
SDRAM Write Recovery Time: 5
Write to Precharge Delay: 15 (If it's Listed)
Command Rate: 2T
DDR2 SDRAM Voltage: 2.1
Advanced voltage control
CPU Vcore offset:_Disabled
DDR2 Termination: 0.5x
CPU to NB HT:____1.200V
NB to SB HT:_____AUTO
NB Core/PCI-E:___AUTO
SB Core/PCI-E:___AUTO
SB Standby core:_+1.500V
Output driver control
CKE:______AUTO
CS/ODT:__1.00X
ADD/CMD:_1.00X
MEMCLK:__1.00X
Chipset Core Voltage: Auto
All other settings are motherboard defaults.
Maximum DDR2 recommended VDIMM: 2.1 Volts
or find it yourself at:
http://www.asktheramguy.com/v3/showthread.php?t=52351
I have not changed my setting yet due to my work, but hopefully it can help.