why can't I lower memory timings?

Just completed new build:
A8N-SLI Premium (rev 1.02,BIOS 1008)
AMD 3700 San Diego (E4)
Corsair TWINX2048-3200c2 rev. 2
eVGA 7800 GT (470/1100)
Antec TP-2 550w

Build went well (first build) and XP installed fine. Why can't I lower the timings to corsair's specs? 2-3-3-6.

specs in BIOS:

Manual
400Mhz.
CAS L. was 3, lowered to 2.5, then 2.0
Tras was 8T, can only lower to 5T, should go to 2T no?
Trcd was/is 3T
Trp was/is 3T
Trc was 11t, can only lower to 7T, should go to 6T, no?
Trfc was/is 13T
Trwt was/is 5T
Twr was/is 3T
Memory Timing was 2T, changed to 1T.
S/W over 4G was/is ENABLED
H/W over 4G was/is ENABLED

Runs through 3Dmark05 fine, score 7460 (good for this combo stock?)
Aquamark3 scored 77,716


I have downloaded memtest86, but haven't used it yet. I might run it overnight but dont know how to use it yet. (have to read up) Any advise?

Thanks

corsairs is
Cas : 2
TRP : 3
tRCD : 3
TRAS : 6

have you tried higher vdimm like 2.7 or 2.8 volts?

ok , I confused the order. doh!

this is how they're listed in my bios: (and where they're set now)


1.) timing mode manual
2.) memory clock 400mhz
3.) cas# 2
4.) Tras 6T
5.) Trcd 3T
6.) Trp 3T
7.) Trc 7T
8.) Trfc 13T
9.) Trwt 5T
10.) Twr 3T
11.) 1T/2T 1T
12.) sw over 4G enabled
13.) hw over 4G enabled

I've lowered settings 1,3,4,5,6 and 11.
should i lower others like trc,trfc,trwt??

thanks

memory specs from cpu-z:

Memory
DRAM Type DDR-SDRAM
DRAM Size 2048 MBytes
DRAM Frequency 201.0 MHz
FSB: DRAM CPU/11
CAS# Latency 2.0 clocks
RAS# to CAS# 3 clocks
RAS# Precharge 3 clocks
Cycle Time (TRAS) 6 clocks
Bank Cycle Time (TRC) 7 clocks
DRAM Idle Timer 16 clocks
# of memory modules 2
Module 0 Corsair DDR-SDRAM PC3200 - 1024 MBytes
Module 1 Corsair DDR-SDRAM PC3200 - 1024 MBytes