Need help with memory settings

[Frag-e-Delic]

First of all my system: P4 2.8Ghz FSB800, Asus P4C800 Deluxe (bios 1011), Corsair TwinX PC3200 LL (2*256MB).

I finally started to manually configure my memory timings. Here are the settings that work:

Jumperfree Configuration:

- AI Overclock Tuner : Manual
- CPU External Frequency : 200
- DRAM Frequency : 400 (1:1 divider)
- AGP/PCI : Frequency : Auto
- CPU Core Voltage : Auto
- DDR Reference Voltage : 2.75v
- AGP VDDQ Voltage : 1.50v
- Performance Mode : Auto

Chipset:

- Configure DRAM Timings by SPD : Disabled
DRAM Cas Latency : 2.5
DRAM Ras Precharge : 3
RAS to CAS : 3
DRAM Precharge : 6
Burst Lenght : 8

- Performance Accelleration Mode : Enabled
- DRAM Idle Timer : Auto
- DRAM Refresh Rate : Auto
- Graphic Adapter Priority : AGP/PCI
- Graphics Aperture Size : 128 MB
- Spread Spectrum : Enabled
- ICH Delayed Transaction : Enabled
- MPS Revision : 1.4

Legacy USB support Disabled.

When I changed Cas Latency to 2, I got a blue screen before I get into Windows (XP). So I changed Cas Latency back to 2.5 and my system booted correctly.
Is there anything else I have to change to get CL 2?