[U-Boot] K9G8G08UM u-boot 1.1.6 saveenv

[hjj]

 Hi,every one ,i met a question with u-boot 1.1.6 and nand flash K9G8G08UM。
when i do saveenv, it can save into ram,but when i reset ,it resets the default!
following is u-boot information:

U-Boot 1.1.6 (Nov  2 2008 - 10:54:43) for SMDK6400


CPU:     S3C6400 at 533MHz
         Fclk = 533MHz, Hclk = 133MHz, Pclk = 66MHz (ASYNC Mode) 
Board:   SMDK6400
DRAM:    128 MB
Flash:   0 kB
NAND:    1024 MB
*** Warning - bad CRC or NAND, using default environment
"*** Warning - bad CRC or NAND, using default environment"

this is the main question!

i hope i can get someone help,thanks very much!