MicroLIB printf problem

Hi everyone,
I am using LPC2468 and put the U-Boot as my boot loader in the on-chip flash, and my application program is not uLinux, it compiles by KEILC with MicroLIB and exist in an external NOR Flash.
After power on reset, the U-Boot will go to my application program, the program will copy U-Boot's environment variables from the on-chip flash sector(0x7C000~0x7CFFF) to on-chip RAM.
Now my application program can read and modify an environment variable, but when I computes the CRC, the result was wrong if I use printf() to show the result. Even though I do not change the data of the environment variables, the problem still occurs. For example:

char AppEnv_UbootDataAllLoad(void)
{
        unsigned char *ptr = (unsigned char*)0x07C000;
        unsigned char *evn_ptr = (unsigned char*)&env_var;
        int i;
        unsigned long tmp = 0;
        unsigned long tmp2 = 0;

        printf("Copying U-Boot Env to RAM..");

        for(i=0; i<0x1000; i++){                             // load data from flash to RAM
                evn_ptr[i] = ptr[i];
        }

        printf(" done.\n\r");

        tmp = crc32(0, env_var.data, ENV_DATA_SIZE);
        printf("crc32:%08X\n\r", tmp);                        // <here>
        tmp2 = crc32(0, env_var.data, ENV_DATA_SIZE);
        printf("crc32_2nd=%08X\n\r",tmp2);

        return 0;
}

This function calls crc32() twice and get diffenet result, but if I don't use the KeilC' MicroLIB, the two crc32() result will be the same. It seems like the printf() will change some RAM data, or there is something I need to setup for my KeilC project with MicroLIB.

Snaku