Could my issue be the same problem as this thread?: http://archives.postgresql.org/pgsql-bugs/2005-11/msg00114.php The references to "Invalid Argument" caught my eye. That thread did start from a very different point, though. -Kevin >>> "Kevin Grittner" <Kevin.Grittner@xxxxxxxxxxxx> >>> It appears that the log file is not being written -- I'll start a separate thread on that issue. I reran the query. Same error, same relation, different block. dtr=> UPDATE dtr-> "DbTranRepository" dtr-> SET "userId" = UPPER("userId") dtr-> WHERE ( dtr(> ("userId" <> UPPER("userId")) AND dtr(> ("timestampValue" BETWEEN '2005-10-28' AND '2005-11-15')); ERROR: could not read block 1118215 of relation 1663/16385/16483: Invalid argument -Kevin ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq