Problem updating duplicate records

guys, I have a CloseDate field in my database that gets populated with a parsed date from a website. When the database is empty and i insert my parsed data into the database, the CloseDate field is populated fine. However once the database is populated and i run the insert on duplicate update, the CloseDate field is populated with 0000-00-00. Why is the CloseDate field getting affected?

Here is my code:
<cfquery name="insJobRecord2" datasource="job">
insert into advertisements (ref, Website, Description, Title, Salary, Location, Contract, CloseDate, IntDate)
values
(<cfqueryparam value="#Links2[i]#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisURL2#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisJD2#" cfsqltype="CF_SQL_LONGTEXT">,
<cfqueryparam value="#thisTitle2#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisSalary2#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisLocation2#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisContract2#" cfsqltype="CF_SQL_VARCHAR">,
<cfqueryparam value="#thisCloseDate2#" cfsqltype="CF_SQL_DATE">,
<cfqueryparam value="#thisIntDate2#" cfsqltype="CF_SQL_VARCHAR">)
on duplicate key update Description = '#thisJD2#', Title = '#thisTitle2#', Salary = '#thisSalary2#', Location = '#thisLocation2#', Contract = '#thisContract2#', CloseDate = '#thisCloseDate2#', IntDate = '#thisIntDate2#'
</cfquery

There are three of these queries, one for each parsed website. I have outputted the thisCloseDate variable for each and they all give me a closedate. However they are slightly different in there format . e.g. 23/05/2005 and 16 May 2005

What database are you using? This might be a question to ask in a forum specific to that database, as I don't see any obvious reason why it would be resetting itself. As far as I know MySQL is the only DB that has "on duplicate key", so you might want to ask in the MySQL forum.

Cheers Kiteless I already posted on MySQL, but I was just checking that it wasnt a CF problem.....thanks anyway