dbimport crashes

IDS 11.5 on RHEL 5. Running a dbimport crashes IDS 11.5 horribly. It's OK on IDS 10.0FC8. even running with an empty schema does it. Anyone seen any such problems? I have a call open: PMR not assigned yet. We get loads of these in the online log . 01:27:13 Assert Failed: Memory block header corruption detected in mt_shm_free 1 01:27:13 IBM Informix Dynamic Server Version 11.50.UC1 01:27:13 Who: Session(23, informix@localhost.localdomain, 6002,0x4c45bb90) Thread(76, sqlexec, 4c434ca0, 1) File: mtshpool.c Line: 3466 01:27:13 Results: Pool not repaired 01:27:13 Action: Please notify IBM Informix Technical Support. 01:27:13 stack trace for pid 5987 written to /opt/informix/11.0/tmp/af.434ed77 01:27:13 See Also: /opt/informix/11.0/tmp/af.434ed77 01:27:15 Memory block header corruption detected in mt_shm_free 1 01:27:15 invoke_alarm(): /bin/sh -c '/opt/informix/10.0/etc/alarmprogram.sh5 6 "Internal Subsystem failure: 'MT'" "Memory block header corruption detected in mt_shm_free 1" ""' Then eventually it gives up the ghost: 01:27:52 Process exited with return code 126: /bin/sh /bin/sh -c /opt/informix/10.0/etc/alarmprogram.sh 2 23 "Logical Log 322 Complete,timestamp: 0xd61ac3." "Logical 01:27:55 stack trace for pid 5987 written to /opt/informix/11.0/tmp/af.434ed77 01:27:55 Assert Failed: No Exception Handler 01:27:55 IBM Informix Dynamic Server Version 11.50.UC1 01:27:55 Who: Session(23, informix@localhost.localdomain, 6002,0x4c45bb90) Thread(76, sqlexec, 4c434ca0, 1) File: mtex.c Line: 475 01:27:55 Results: Exception Caught. Type: MT_EX_OS, Context: mem 01:27:55 Action: Please notify IBM Informix Technical Support. 01:27:55 See Also: /opt/informix/11.0/tmp/af.434ed77 01:27:57 mtex.c, line 475, thread 76, proc id 5987, No Exception Handler. 01:27:57 invoke_alarm(): /bin/sh -c '/opt/informix/10.0/etc/alarmprogram.sh5 6 "Internal Subsystem failure: 'MT'" "mtex.c, line 475, thread 76, proc id 5987, No Exception Handler." ""' 01:27:57 invoke_alarm(): mt_exec failed, status 32256, errno 0 01:27:58 The Master Daemon Died 01:27:58 invoke_alarm(): /bin/sh -c '/opt/informix/10.0/etc/alarmprogram.sh5 6 "Internal Subsystem failure: 'MT'" "The Master Daemon Died" ""' 01:27:58 invoke_alarm(): mt_exec failed, status 32256, errno 0 01:27:58 PANIC: Attempting to bring system down -- Neil Truby t:01932 724027 Director m:07798 811708 Ardenta Limited e:neil.truby@ardenta.com