I searched about this and get across a thread about this problem (link)
I followed mentioned commands in thread using adb:
# cd /sdcard/clockworkmod/backup/2010-06-188.8.131.52
# rm nandroid.md5
# md5sum *img > nandroid.md5
Now on the last command adb saying that 'md5sum not found'. cant figure out the problem.
One post I saw somewhere told me to install busybox and try command '# busybox md5sum *img > nandroid.md5'. But that also gone in vain.