the problem can be found in line 570 of the file zabbix-1.4.6/upgrades/dbpatches/1.4/mysql/patch.sql
the columns are not correctly mapped between items_tmp and the subquery "select *,'','' from items". the columns of the subquery are ordered alphabetically. those are mapped in into items_tmp with the order in which those columns where specified in the "create" statement. this results in the following mapping:

itemid \=> itemid
type \=> type
snmp_community \=> snmp_community
snmp_oid \=> snmp_oid
snmp_port \=> snmp_port
hostid \=> hostid
description \=> description
key_ \=> key_
delay \=> delay
history \=> history
nextcheck \=> trends
lastvalue \=> nextcheck
lastclock \=> lastvalue
prevvalue \=> lastclock
status \=> prevvalue
value_type \=> status
trapper_hosts \=> value_type
units \=> trapper_hosts
multiplier \=> units
delta \=> multiplier
prevorgvalue \=> delta
trends \=> prevorgvalue
snmpv3_securityname \=> snmpv3_securityname
snmpv3_securitylevel \=> snmpv3_securitylevel
snmpv3_authpassphrase \=> snmpv3_authpassphrase
snmpv3_privpassphrase \=> snmpv3_privpassphrase
formula \=> formula
error \=> error
lastlogsize \=> lastlogsize
logtimefmt \=> logtimefmt
templateid \=> templateid
valuemapid \=> valuemapid
_ \=> delay_flex
_ \=> params

e.g. the trends column will contain the values of the nextcheck column after the upgrade.