Lock submit button

[DWZ]

I want the "Submit new thread" and "Preview Post" button to lock whenever someone clicks it. I found some JavaScript for a generic form on the internet and tried to get it to work with vBulletin.

The original code was:<script language="JavaScript">
function dis(obj)
{
for(i=0;i<obj.length;i++)
if(obj.elements[i].type == "submit" || obj.elements[i].type == "reset")
obj.elements[i].disabled = true;
}
</script>[/code]I changed that too:[code]<script language="JavaScript">
function dis(obj)
{
for(i=0;i<obj.length;i++)
if(obj.elements[i].type == "submit" || obj.elements[i].type == "preview")
obj.elements[i].disabled = true;
}
</script>

I then added the following just after my body tag:

<form onsubmit="return dis(this)">

Now, the button locks when you click it, but it wont post the thread or reply, it takes you to some strange URL, for example:

http://localhost/forums/newreply.php...52&attachment=


and the post is never submitted.

Any ideas?