403 Forbidden error when trying to post javascript in block or module

I wish to put the following html in a block (external js resource) but everytime I try to submit it I get a 403 error. If I take out the script tag it submits OK.

<script language=javascript type="text/javascript"
src="http://ss.webring.com/navbar?f=j;y=xyz;u=98368265">
</script><noscript><center>
<table bgcolor=gray cellspacing=0 border=2><tr>
<td><table cellpadding=2 cellspacing=0 border=0><tr><td align=center>
<font face=arial size=-1>This site is a member of WebRing. 
<br>To browse visit <a href="http://ss.webring.com/navbar?f=l;y=xyz;u=98368265">
Here</a>.</font></td></tr></table></td></tr></table>
</center></noscript>

I believe from reading other posts that it's not really a 403 error but the error displays as a 403 error???. I have diabled tinymce and spam modules but to no avail. I have tried using a 'blank' input filter and a 'full html' input filter but the same thing happens. I also can't post this code in a forum post or content etc...

Any ideas what I need to do to get it to work?

Thanks, Matt