[U-Boot] K9G8G08UM u-boot 1.1.6 saveenv

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@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!