[Zope] ObjectManager problem

[Max Møller Rasmussen]

I am making a product that draws a graph in PIL and then saves the image as
a GIF in a Zope ObjectManager.

If the image doesn't exist it will be rendered and saved in the
objectManager.

When I run it the first time the image renders just nicely in a dmtl page.
If I try to reload it, I get an error that says::

Error Type: Bad Request
Error Value: The id "laeringsGraf" is invalid--it is already in use.
...

  File C:\zope23\lib\python\Products\ots_laering\ots_laeringLogic.py, line
207, in updateGraph
    (Object: laering)
  File C:\zope23\lib\python\Products\ots_laering\ots_laeringLogic.py, line
196, in _drawTriangle
    (Object: laering)
  File C:\zope23\lib\python\OFS\ObjectManager.py, line 272, in _setObject
    (Object: laering)
  File C:\zope23\lib\python\OFS\ObjectManager.py, line 147, in checkValidId
    (Object: laering)

So it seems that the Image gets saved OK ... somewhere, but I cannot se the
id via self.objectIds() which simply returns an empty tuple ().

My object inherits ObjectManager, but it doesn't seem like the Image gets
saved in it. 

I can see it in a dtml page like <dtml-var laeringsGraf> but apparantly it's
saved somewhere else .... I'm completely baffled.

I check for existance of the image like so::

    def updateGraph(self):
        "Render graf if it doesn't exist"
        imageID = 'laeringsGraf'    
        print 'objects:', self.objectIds()
        if imageID in self.objectIds(): # allready exists
            pass
        else:                           # doesnt exist, so render first time
            self._drawTriangle([150, 0, 0, 0], 10, 10)

The following is the snippet of code that saves the image from PIL into the
ObjectManager

        # save it in the ZODB
        outf = StringIO()
        im.save(outf, 'GIF')
        del im
        
        data = outf.getvalue()
        outf.close()
        imageID = 'laeringsGraf'
        self._setObject(imageID, OFS.Image.Image(imageID,'Lærings graf',''))
        self._getOb(imageID).update_data(data)

Anybody's got a clue??? Please.

Regard Max M