[U-Boot] mpc837x,u-boot1.3.3,dead in unlock_ram_in_cache()

[allen.lotus]

hi:
    all,i used mpc837x chip and u-boot1.3.3,the uboot could start normally,but when i use command "tftp" and "bootm" download the linux 2.6.25 uImage and dtb,the uboot could download these file to RAM.but before uboot transfer control to linux,it wil execise unlock_ram_in_cache(),which is in  cmd_bootm.c.and the uboot will die in this function,sometime it will reboot from this function.
    i do not know why?the unlock_ram_in_cache() funciton itself should no problem,where should i check or which macro should i check?
how to avoid this problem? i want to let my kernel run as soon as possible!
    please help me,everione!