Can not signin with username is number

[hernancorteshc@hotmail.com]

Hi!
Finally I prepended a letter to the beginning of the username (not so behind de scenes but it works).
Added a script to "users\login.php" just before the html form declaration. And inside the form tag I added onsubmit="addText()":

<script type="text/javascript">
function addText() {
var input = document.getElementById('username');
input.value = 'u' + input.value;
}
</script>

<form name="login" class="form-signin" action="login.php" method="post" onsubmit="addText()">

That's it. Not the better solution but it works for now.
Thank you very much!
Hernan