hi
swoog (192.168.50.11[192.168.50.11]) - ProFTPD terminating (signal 11) Does it ring a bell ?
There is no sufficient information, perhaps you must up the debug level (try -d 9). If you can't see the error, try to run it without mod_ldap configuration (using your system users).
If nothing works you can use a strace command (system call tracer) to obtain more data. The most simple use is strace -p <proftpd_PID>
good luck