FULL PRODUCT VERSION :
java version "1.6.0_06"
Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
Java HotSpot(TM) Client VM (build 10.0-b22, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Linux porro 2.6.24-19-generic #1 SMP Fri Jul 11 23:41:49 UTC 2008 i686 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
JSpinner does not remove listener connections to existing models when a new model is set using setModel(). The code in question:

    public void setModel(SpinnerModel model) {
        if (model == null) {
            throw new IllegalArgumentException("null model");
        }
        if (!model.equals(this.model)) {
            SpinnerModel oldModel = this.model;
            this.model = model;
            if (modelListener != null) {
                this.model.addChangeListener(modelListener);
            }
            firePropertyChange("model", oldModel, model);
            if (!editorExplicitlySet) {
                setEditor(createEditor(model)); // sets editorExplicitlySet true
                editorExplicitlySet = false;
            }
            repaint();
            revalidate();
        }
    }

Clearly lacks the necessary oldModel.removeChangeListener(modelListener).

I have recently found very similar bugs in three different swing components, so I would suggest checking through other components as well for similar bugs, as these "dropped" listener connections can cause quite some memory leakage and slowdown.


REPRODUCIBILITY :
This bug can be reproduced always.