You probably got a bad stick. Are you on bios 1.1.11?
I actually upgrade 1gb at a time from 4gb -- I didn't want to go opening sticks that wouldn't work.
Presently, I have:
DIMM # 1
SMBus address 0x50
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Centon (7F7F7F1900000000)
Size 2048 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number MICT38UXB 2GB
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP yes (0 profiles)
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 3.0-3-3-9-12 @ 200 MHz
JEDEC #2 4.0-4-4-12-16 @ 266 MHz
JEDEC #3 5.0-5-5-18-24 @ 400 MHz
DIMM # 2
SMBus address 0x51
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Crucial Technology (7F7F7F7F7F9B0000)
Size 2048 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number CT25664AA800.M16FH
Manufacturing date Week 25/Year 11
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 4.0-4-4-12-16 @ 266 MHz
JEDEC #2 5.0-5-5-15-20 @ 333 MHz
JEDEC #3 6.0-6-6-18-24 @ 400 MHz
DIMM # 3
SMBus address 0x52
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Kingston (7F98000000000000)
Size 2048 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number
Serial number 6720F179
Manufacturing date Week 25/Year 11
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 4.0-4-4-12-16 @ 266 MHz
JEDEC #2 5.0-5-5-15-20 @ 333 MHz
JEDEC #3 6.0-6-6-18-24 @ 400 MHz
DIMM # 4
SMBus address 0x53
Memory type DDR2
Module format Regular UDIMM
Manufacturer (ID) Kingston (7F98000000000000)
Size 2048 MBytes
Max bandwidth PC2-6400 (400 MHz)
Part number
Serial number 6520079B
Manufacturing date Week 25/Year 11
Number of banks 2
Data width 64 bits
Correction None
Nominal Voltage 1.80 Volts
EPP no
XMP no
JEDEC timings table CL-tRCD-tRP-tRAS-tRC @ frequency
JEDEC #1 4.0-4-4-12-16 @ 266 MHz
JEDEC #2 5.0-5-5-15-20 @ 333 MHz
JEDEC #3 6.0-6-6-18-24 @ 400 MHz
It all works very well, despite having mixed manufacturers and timings. I bought whatever CompUSA had on sale every few weeks
I've run Linux's memory test for hours with no errors -- so overall, it's been a total success!