I created a very simple custom webpart which is modified by a very simple custom editor.
I am using the same web part on one page several times in an attempt to improve administration....
When I click apply / ok my changes seem to be made without a problem.
However, when I edit another instance (ie. change CustomPart1 and save and then go to change CustomPart2) the changes for the first instance (CustomPart1) are lost.

Any ideas?

public override bool ApplyChanges( )
        {
            ProductObject product       = new ProductObject( );
            product.BodyText            = txtBody.Text;
            product.HeaderText          = txtHeader.Text;
            product.ImageUrl            = txtImageUrl.Text;
            product.NavigateUrl         = txtNavigateUrl.Text;

            ProductPart.Update( product );
            
            return true;
        }

public void Update( ProductObject p )
        {
            this.SetPersonalizationDirty( );
            this.Product = p;
            CreateChildControls( );
        }

void IPersonalizable.Load( PersonalizationDictionary state )
        {
            PersonalizationEntry pe = state[ "Test" ] as PersonalizationEntry;

            if( pe != null )
            {
                this.Product = ( ProductObject )pe.Value;
            }
        }

        void IPersonalizable.Save( PersonalizationDictionary state )
        {
            PersonalizationEntry entry = new PersonalizationEntry( this.Product, this.WebPartManager.Personalization.Scope );
            state[ "Test" ] = entry;
        }

Nevermind I figured it out.
It had to do with the PersonalizationScope.