[jQuery] unknow wrror

[jQuery] unknow wrror


Hi all!
I try to make an application with ajax.
I need a input field with typewatch plugin. If the user stop the type
the TypeWatch call an php function through $.getJSON().
The ajax call workig fine. The result come back. I can see in Firebug
but i have an error message (bottom). What is the error? Did I
something wrong?
"uncaught exception: [Exception... "Could not convert JavaScript
argument" nsresult: "0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)"
location: "JS frame :: http://.../jquery.js ::
anonymous :: line 238" data: no]"
here is my javascript code:
$("#makeorder_testing_negation_term_start").typeWatch(
    {highlight:true,callback:negation_term_start}
);
function negation_term_start(txt){
    $("#makeorder_testing").html(
        $.getJSON("grid/test",function(txt){$("#makeorder_texsting").html(txt)})
    )
};
Thanks the help!
András
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