Normal app made into MDI-app, now Open doesn't work?

Yesterday I changed my app from a one form app into an MDI application. I did
this by simply copying the form and taking everything out of the form that
didn't belong in there (I used the Demo-app 'TextEdit' which came with Delphi
2.0) as an example.

I made the MainForm the MDIform and the MDIForm the MDIChild.. Everything seems
to work fine, accept opening files. I get the error 'EFOpenError, couldn't open
*.txt'.. I suspect the problem had to do with the way I try to open, but it's
the same as in a Demo program 'Text Edit'.. In the MainForm:

Procedure OpenButton1Click(Sender: TObject);
with MDIForm.Create(Self) do
Open(OpenDialog1.FileName);

In de MDIForm:

procedure Open(const AFileName: string);
PathName := AFileName;
with RichEdit1 do
Lines.LoadFromFile(AFileName);
etc..

What could be the problem?
Thanx in advance for any suggestions.

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