Initialisation error Error calling method on NPObject! [plugin exception: java.lang.IllegalArgumentException: No method found matching name newInstance and arguments [com.sun.java.browser.plugin2.liveconnect.v1.JavaNameSpace, java.lang.Integer]].

I think I have previously deleted Java 6 Update 7 and this has now thrown up the above message.

Anyone advise what to do? I have un- and reinstalled Firefox and the Freecycle add on. What now?