SQL Developer Data Modeler

I am using Data Modeler 3.0.0.665 (Java 1.6.0_24) on Windows 7 Professional.

I am trying to use data modeler to create relationship diagrams for an existing database.

I have imported objects from an existing database into the relational model, then created a logical model from this and finally built a multidimensional model with cubes, dimensions, hierarchies and levels.

When I reopen data modeler and view the multidimensional model diagram, some of the objects (cubes, dimensions, levels) and no longer displayed. I can see the relationship lines and spaces for the objects, but not the objects themselves. When I click on the space for the object, it appears, but then vanishes if I selection something else. If I hover over objects, or resize the screen, maximise the window, etc - some of the objects will suddenly appear again, or vanish. I dont seem to have any control over what is shown or hidden. Sometimes by clicking on all objects individually I can get the model to display all objects, but only temporarily as they will inevitablly vanish again.

If I try to print the diagram - it omits all the hidden objects.

I dont seem to have the same problem with logical or relational model displays.
I've looked through the forum and seen a similar issue related to a logical model display but there was no resolution.

I've looked in the datamodeler.log file and there dont seem to be any errors.

Any help or suggestions with this would be most welcome.