Unable to drop RdB database

[Thomson, Martyn EDUC:EX]

Hi Listers. Not exacly a PH question but related...
I am attempting to drop an Oracle RdB V7.2 database but can't -
SQL> drop database filename SLD.RDB;
%RDB-E-LOCK_CONFLICT, request failed due to locked resource
-RDMS-F-LCKCNFLCT, lock conflict on client 'DDL' 4C444400000055

$RMU/SHOW lists - 
   - 1 active database user on this node
      - 218C3B93:1 - SLDDRD036000B72, EDUC_SLW_SQS
        - attached  8-JAN-2008 12:49:31.43 (elapsed 0 00:00:02)
        - image $1$DGA1:[SYS1.SYSCOMMON.][SYSEXE]RDB$NATCONN72.EXE

If I try to close the database - 
$rmu/close/abort/network SLD_RDB_DATABASE

...this "user" immediately reconnects.

Can anyone tell me what this is and if it's safe to kill it - and how to kill it?
TIA,
Regards, Martyn