coldfusion flash integration: I have a problem using cfgrid.

I'm getting the following error message:
?Error casting an object of type to an incompatible type. This usually
indicates a programming error in Java, although it could also mean you have
tried to use a foreign object in a different way than it was designed.?

The error occurs when I run this code:

<cfif IsDefined("form.gridEntered")>
<cfgridupdate grid="FirstGrid" dataSource="#dsn#" Keyonly="true"
tableName="tblManager">
</cfif>

It is connecting to a mySQL 4.1 database.

I think the problem is to do with a field I've added called ?Active? of
datatype INT(1). I am using this as a boolean as as far as I'm aware, this is
the nearest equivalent in mySQL.

In my <cfgrid> I have added the following column.

<cfgridcolumn name="Active" type="boolean" display="yes" width="40"
header="On" bold="true" />

Which shows a tickbox and is the look I want to achieve on the grid.
I think this is causing the Java error. What do I need to do to allow
submission to the grid of this datatype, please?

Thank you for your time and help.

To answer my own question on this...