WebMarkupContainer and SimpleAttributeModifier problems on 1.4.1 upgrade.

[VGJ]

I've got a little helper method for replacing HTML tag attributes:

    public static WebMarkupContainer getContainer(
            String name,
            String attribute,
            String value)
    {
        //modify check add-on img tag
        WebMarkupContainer container = new WebMarkupContainer(name);
        container.add(new SimpleAttributeModifier(attribute, value));

        return container;
    }

I just upgraded from 1.3.2 to 1.4.1, and I'm getting this exception every
time the above method calls the "add" method:

"java.lang.NoSuchMethodError:
org.apache.wicket.markup.html.WebMarkupContainer.add(Lorg/apache/wicket/behavior/IBehavior;)Lorg/apache/wicket/Component;"

I just looked at the 1.4 Javadocs...it looks like this is still valid.  What
am I doing wrong?

Thanks!

-v