Assert Failed: Buffer modified in inconsistent chunk

Dear People, We are running I-Online 7.10.UD1 on HP-UX 10.01 and recently encountered the following error/problems: ---- start error message --------------- 15:54:14 Logical Log 1136 Complete. 15:55:52 Checkpoint Completed: duration was 31 seconds. 15:57:31 Checkpoint Completed: duration was 30 seconds. 15:57:46 Assert Failed: Buffer modified in inconsistent chunk. 15:57:46 Who: Session(8012, informix@unknown, 10364, 61) Thread(9148, sqlexec, c1c59ae8, 1) 15:57:46 Results: Chunk 4 is being taken OFFLINE. 15:57:46 Action: Restore chunk from archive. 15:57:46 See Also: /home4/af.67d6cec, shmem.67d6cec.0 15:57:56 Assert Failed: WARNING! Chunk 4 is being taken OFFLINE. 15:57:56 Who: Session(8012, informix@unknown, 10364, 61) Thread(9148, sqlexec, c1c59ae8, 1) 15:57:56 Results: DBspace koperkasadbs is disabled. 15:57:56 Action: Restore DBspace koperkasadbs 15:57:56 See Also: /home4/af.67d6cec 15:57:56 Assert Failed: Page Check Error in getslot:bad page 15:57:56 Who: Session(8012, informix@unknown, 10364, 61) Thread(9148, sqlexec, c1c59ae8, 1) 15:57:56 Results: Possible inconsistencies in 'TBLSpace 2097360' 15:57:56 Action: Run 'oncheck -cD 2097360' 15:57:56 See Also: /home4/af.67d6cec 16:02:35 Checkpoint Completed: duration was 0 seconds. 16:11:40 Shutdown Mode ---- end error message ---- Could someone kindly explain the possible causes of the chunk to be inconsistent as we have perform the oncheck a few days earlier before this incident. Furthermore, after restoration (and loss of some data) the database is back to normal order. Additional preventive steps are also welcomed. Thanks for helping. Regards Richard W Sinyem