The problem occurs only when the provision is not in the default path (ie. /usr/local/samba/private) and that the path to the correct configuration file has not been supplied.
The stack trace is the following:
Continuing.
FIXME: Using new system session for hdb
talloc: double free error - first free may be at ../kdc/db-glue.c:1321
Bad talloc magic value - double free

Program received signal SIGABRT, Aborted.
0xb7fd3416 in __kernel_vsyscall ()
(gdb) bt
#0  0xb7fd3416 in __kernel_vsyscall ()
#1  0xb72ee800 in raise () from /lib/i686/nosegneg/libc.so.6
#2  0xb72f02d8 in abort () from /lib/i686/nosegneg/libc.so.6
#3  0xb7737865 in talloc_abort () from /usr/local/samba/lib/libtalloc-samba4.so.2
#4  0xb773791c in talloc_abort_double_free () from /usr/local/samba/lib/libtalloc-samba4.so.2
#5  0xb7737a2a in talloc_chunk_from_ptr () from /usr/local/samba/lib/libtalloc-samba4.so.2
#6  0xb7738fcd in _talloc_free () from /usr/local/samba/lib/libtalloc-samba4.so.2
#7  0x08059ce5 in samba_kdc_firstkey ()
#8  0x080529ce in hdb_samba4_firstkey ()
#9  0x080553e7 in hdb_next_entry ()
#10 0xb7b41856 in krb5_kt_next_entry () from /usr/local/samba/lib/libldb-samba4.so.0
#11 0xb7b6817e in kt_copy () from /usr/local/samba/lib/libldb-samba4.so.0
#12 0xb69d07d9 in libnet_export_keytab () from /usr/local/samba/lib/python2.5/site-packages/samba/net.so
#13 0xb697add5 in py_net_export_keytab () from /usr/local/samba/lib/python2.5/site-packages/samba/net.so
#14 0xb747cb79 in PyCFunction_Call () from /usr/lib/libpython2.5.so.1.0
#15 0xb7443a17 in PyObject_Call () from /usr/lib/libpython2.5.so.1.0
#16 0xb74cd21d in PyEval_EvalFrameEx () from /usr/lib/libpython2.5.so.1.0
#17 0xb74d0edd in PyEval_EvalCodeEx () from /usr/lib/libpython2.5.so.1.0
#18 0xb74676d9 in ?? () from /usr/lib/libpython2.5.so.1.0
#19 0x08199068 in ?? ()
#20 0x08195d74 in ?? ()
#21 0x00000000 in ?? ()