Some files display error and directory can‘t be deleted

[pchen123]

Hi,
I do a test for create directory and file in the usb device,after created it ,will delete the file and directory. About 3 weeks later，the test stops and one directory can not be deleted,do command "ls" in the directory，display "No such file or directory".
/mnt/rwfs/media/sda1/Recorder # rm -rf 20204648
rm: can't remove '20204648': Directory not empty
/20204648 # ls
ls: ./15_2307879#_303_20204648_0513105613_402__cd_recvW674.dat: No such file or directory
ls: ./15723078793__03_20204648_05_3505613_4024_cd_recv_675.dat: No such file or directory

My system is Embedded linux system,kernel version is 2.6.36.
in the printk,displayed the message:
"convert_uni_to_ch: fail to use nls"

The problem had happened 2 times, Do you know the cause of the problem?

Thank you
Michael