exec cp failes from script, yet works when issued directly

I have a script that copies SQL backups to a windows server. Here's the line from /etc/fstab: //my.win.box/share$ /winshare cifs credentials=/etc/credfile,dom=mydomain,uid=0,gid=0,file_mode=0600,dir_mode=0700 0 0 Here's the backup script: backup.sh: # copy zipped sql exports to /winshare/db find /backups/sql/*sql.gz -mtime +1 -exec cp {} /winshare/db \; Logged in with root privileges (in this case, as root) $ ./backup.sh cp: cannot create regular file `/winshare/db/mydb_20130301.sql.gz': Permission denied Yet if I issue the command from a prompt, rather than through the script: $ find /backups/sql/*sql.gz -mtime +1 -exec cp {} /winshare/db \; The file(s) are copied as expected. Again, logged in as root here. What could be causing the in-script command to fail, yet the identical command to work from console?