just for testing, remove the java script code from your login form:
like this one:
//submit the form if the user presses the ENTER key
function checkEnter(event)
{
var code = 0<br/>
<br/>
if (NN4) {<br/>
code = event.which<br/>
} else {<br/>
code = window.event.keyCode<br/>
}<br/>
<br/>
if (code==13)<br/>
document.forms[0].submit()<br/>
}