Index Corruption - Online V5.02.UC1

We are running Informix Online V5.02.Uc1 on HP-UX. We recently faced an Index Corruption problem and after tbchecking we dropped and recreated the Index and things are back to normal. The activity on the table was normal. The table sees only insert and query activity. (No updates/deletes/index modifications). The table had about 78000 rows and the chunks reside on LVM disks. The index is made up of two fields and uses a descending clause. What I would like to know is a) what are the situations under which such a corruption occurs and b) what ( if any) are the steps that can be taken to eliminate/minimize such occurences. Thanks for all responses Raj