Simulations with OMEGA BLOCK

Hi NMUSERS, I have a question regarding the use of OMEGA BLOCK statements in simulations when one (or more) elements of the matrix are 0. When I use the following lines to describe the OMEGA structure and run the simulation everything works well: $OMEGA 0 FIX ; IIV_CL2 0.1 ; IIV_V2 0.1 ; IIV_F1 0.01 ; IIV_KA $OMEGA BLOCK(1) 0.01 ; IOV_KA $OMEGA BLOCK(1) SAME $OMEGA BLOCK(1) SAME $OMEGA BLOCK(1) SAME However, rewriting the above as a full matrix gives me an error message: $OMEGA BLOCK(8) 0 FIX 0 0.1 0 0 0.1 0 0 0 0.01 0 0 0 0 0.01 0 0 0 0 0 0.01 0 0 0 0 0 0 0.01 0 0 0 0 0 0 0 0.01 NM-TRAN MESSAGES AN ERROR WAS FOUND IN THE CONTROL STATEMENTS. AN ERROR WAS FOUND ON LINE 75 AT THE APPROXIMATE POSITION NOTED: 0 0 0 0 0 0 0 0.01 224 A VARIANCE IS ZERO, BUT THE BLOCK IS NOT FIXED TO ZERO. I tried numerous different ways of placing the term FIX in the block, or not mentioning it at all - nothing worked, except replacing the 0 diagonal element by a very small number. I know that there are certain constrains of using 0 values in an OMEGA BLOCK (band symmetric form), but I always thought this was only relevant for estimation. Has anyone come across a similar issue when simulating? Best regards, Andreas. Andreas Lindauer, Ph.D. Associate Principal Scientist, Clinical PKPD Pharmacokinetics, Pharmacodynamics, and Drug Metabolism Merck & Co. / MSD Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station, New Jersey, USA 08889), and/or its affiliates Direct contact information for affiliates is available at http://www.merck.com/contact/contacts.html) that may be confidential, proprietary copyrighted and/or legally privileged. It is intended solely for the use of the individual or entity named on this message. If you are not the intended recipient, and have received this message in error, please notify us immediately by reply e-mail and then delete it from your system.