“ We are seeing lots of errors in the Samba logs, like: ”

tdb(/usr/local/samba_2.2.7/var/locks/locking.tdb): rec_read bad magic
 0x4d6f4b61 at offset=36116

“ What do these mean? ”

This error indicates a corrupted tdb. Stop all instances of smbd, delete locking.tdb, and restart smbd.