If you have a new HD or a new partition and you are trying to add it as a samba share you might run into some problems. Check your log files if you see an error message like
SELinux is preventing smbd (smbd_t) "search" to (file_t)
. Just log in as root and do
# restorecon -v /mnt/newdrive
the -v option tells it to give a verbose output of whatever its doing. You should be able to access your shares now. This puzzled me for a minute because I could still access other shares on the older partition/drive and even new ones as long as they were on the older drive but any new shares on new drive/partition were inaccessible.