HELP! My login script doesnt work on MAC

[Noel 4 DMB]

And it appears to happen when there are spaces in the user name. Here is my form:

PHP Code:

     <table border=0 cellspacing=2 cellpadding=2 colspan=3 class=smallText style="color: #999DB8;">
      <tr>
       <script type="text/javascript" src="/forums/clientscript/vbulletin_md5.js"></script>
       <form name="vblogin" action="/forums/login.php" method=post onsubmit="md5hash(vb_login_password, vb_login_md5password, vb_login_md5password_utf, 0)">
       <td valign=top align=right>username:<br><input type="text" style="width: 80px;" class=input_login name="vb_login_username" id="navbar_username" accesskey="u"></td>
       <td valign=top align=right>password:<br><input type="password" style="width: 80px;" class=input_login name="vb_login_password" accesskey="p"></td>       
       <td valign=bottom align=right>
       <input class=input_login type=submit value="Login" accesskey="s" style="margin-bottom: 2px; padding: 0px; text-align: center;">
       <input type="hidden" name="cookieuser" value="1" id="cb_cookieuser_navbar" accesskey="c">
       <input type="hidden" name="url" value="<? echo $_SERVER['REQUEST_URI']; ?>"> 
       <input type="hidden" name="s" value="" />
       <input type="hidden" name="do" value="login" />        
       <input type="hidden" name="vb_login_md5password" />
       <input type="hidden" name="vb_login_md5password_utf" />
       </td>
       </form>
      </tr>
     </table>

What the heck is wrong?