Weird ISQL problem

Hello all; I have a very unsettling problem with ISQL 4.00.UH1 on a SPARCStation ELC running SunOS 4.1.1. I have a large table that starts off life with 191094 data records in it; I then build an index and run a few update commands, during the course of which the table becomes corrupted!!! If I run "repair table", I lose a few rows: BCHECK C-ISAM B-tree Checker version 4.00.UH1 Copyright (C) 1981-1989 Informix Software, Inc. Software Serial Number LEX#F135736 C-ISAM File: stand.dbs/stand__178 Checking dictionary and file sizes. Index file node size = 1024 Current C-ISAM index file node size = 1024 Checking data file records. Checking indexes and key descriptions. Index 1 = unique key 0 index node(s) used -- 1 index b-tree level(s) used Checking data record and index node free lists. ERROR: 420 missing data record pointer(s) Fix data record free list ? yes Recreating data record free list. 2 index node(s) used, 4136 free -- 190674 data record(s) used, 421 free This behaviour has manifested itself at several past points in this process. I have been diligently searching for an update statement that causes the table to "become corrupt", but so far relatively random rearrangements make the problem go away or appear somewhere else. For those who might wonder why I'm posting rather than going through the normal support route, that's a long story that some nice person at Informix is trying to sort out for me right now. Any comments? Any and all help MUCH appreciated, Chris Hermansen Timberline Forest Inventory Consultants Voice: 1 604 733 0731 302 - 958 West 8th Avenue FAX: 1 604 733 0634 Vancouver B.C. CANADA clh@tfic.bc.ca V5Z 1E5 C'est ma facon de parler.