It is quite likely that the object you are evaluating just does not have a 'value'.
Try using this in theTruClient arguments editor for the "Evaluate JS on Object" to find out:
var typeOBJ = typeof object; window.alert('type is' + typeOBJ + 'id is ' + object.id + ' name is ' + object.name + ' innerHtml is ' + object.innerHTML);
Also, I find Firebug + FirePath to be invaluable. Use Firepath for example to get this XPath
.//*[@id='FORMLOGINid']
Then use the Firebug console to get the object
var element = document.evaluate( ".//*[@id='FORMLOGINid']" ,document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null ).singleNodeValue;
then look at the contents, for example element.id is "FORMLOGINid"
Hope this helps ...