check the sd card mount correct or not and check also its properties about the sdcard (755), we may mount the sdcard to /mnt or something else when system boot up. method as below, in init.rc file , before below setting
setrlimit 4 -1 -1
write /proc/sys/kernel/core_pattern /mnt/sdcard/core.%e.%p
write /proc/sys/fs/suid_dumpable 1
do below setting:
mount /dev/mmcblk0p1 /mnt/sdcard
chmod 755 /mnt/sdcard.
i think it should be OK.