SQL Update then Memo fields disappear

Hello

I am using an SQL statement to update a field in a table that contains a
memo field. When I run the query, then some of the memo data disappears
(Gone forever).
The SQL statement is updating as expected, and no errors are generated.

Why is this happening?
I can see that the memo fields that disappear write (Memo) in a DBGrid and
the memo fields that don't disappear write (MEMO).

Here's the SQL but any update will do this

Update 'c:\demo.DB'
Set Name = 'Steffen Kristensen'
where Number > 1010

On my sample application to generate the error I only have the following
objects:

TTable
TDataSource1
TQuery1
TDbgrid1

I'm using Delphi 5.1 on Windows 2000 with Idapi32.dll 5.1.0.4.
Any help is highly appreciated, because I have absolutely no idea about
what's wrong.

Steffen Kristensen