Memo Field Truncated on Update from Form

I have a form that I am using to append a memo field.  The user clicks a 
button which executes the following:

DoCmd.SetWarnings False

DoCmd.OpenQuery "AppECNItem"

DoCmd.SetWarnings True

--
The AppECNItem sql is:
INSERT INTO tblECNItems ( Item, Rev, Description, [Item Type], 
DispositionInProcess, DispositionInInventory, DispositionInField, 
ChangeDescription, ECNId, NewRev, [Zone], InterChange )
SELECT [forms].[frmecn].[txtitem] AS Expr1, [forms].[frmecn].[txtrev] AS 
Expr2, [forms].[frmecn].[txtdescription] AS Expr3,
[forms].[frmecn].[cmbtype] 
AS Expr4, [forms].[frmecn].[cmbInprocess] AS Expr6, 
[forms].[frmecn].[cmbInventory] AS Expr7, [forms].[frmecn].[cmbInfield] AS

Expr8, [forms].[frmecn].[txtChangeDescription] AS Expr9, 
[forms].[frmecn].[txtECNNo] AS Expr10, [forms].[frmecn].[txtNewRev] AS
Expr5, 
[forms].[frmecn].[txtZone] AS Expr11, [forms].[frmecn].[cmbInterPrior] AS 
Expr12;

--
The memo field is ChangeDescription in the table, or, txtChangeDescription

in the form.  The problem is when appending, I am losing text.  For
instance 
a user might type in 1000 character which get truncated to 500.  

What is causing the truncation and what can i do to fix it.

Thanks, MT