Cant Login on first try, Error: browser does not support cookies on IE & Firefo

[dunccs]

I hav installed RC2, on LAMP, when i customise the login page, i get the error, "Your Browser does not support cookies" on first login, on second login it goes thru. On first login, if i check for the cookie i see it bt smhw it fails bt on second login, goes thru no problem.Yes cookies are enabled. Evrytime after that its fine. Frm a different machine its the same issue. Another thing is i have a javascript code on the login page to join the username and domain part b4 submiting to RC. I hav checked and it works great.Here is the Javascript code and login page code. Your 5cents please???
function validate()
{
var user=document.form._user.value
var domain=document.getElementById("domain").value
var pass=document.getElementById("rcmloginpwd").value
submitOK="true"

txt= "@";
document.form._user.value = user+txt+domain;

if (domain == "10")
 {
 alert("Select A Domain")
 submitOK="false"
 }
if (user == "")
 {
 alert("Please Enter Username")
 submitOK="false"
 }
 if (pass == "")
 {
 alert("Please Enter Password")
 submitOK="false"
 }
if (submitOK=="false")
 {
 return false
 }
}

Login Form

               
               
               Username
               
               @
               
                -- select domain --
                domain1.com
                 domain2.com
                 
               Password