Javascript Reduceing Lag

I have this contact form (cathering.co.uk/contact.php)

In FireFox And IE6 Is creates huge lag when you fill in the last field that it validates I think it dose it because in order to check if the form has been correctly filled out I have a put a SetTimeOut() to the funt that disables and undisables the Send button according to if its been filled in correctly but once its called it goes into a loop by using SetTimeOut(); I narrowed it down to that being the source of the lagginess i tried slowing it down from 1 millisecond to 50 milliseconds it didet really help alot I know its the javascript because i removed the JS file and it worked with out any lag, but even after doing that it still had mass lag ( The Program Just became inrespondive) Any ideas to stop the lag?

Also if i slow it down to more than 500 milliseconds it can be open to people clicking the submit button in time .

Heres javascript code:

var re = new RegExp("[a-zA-Z]");
var disable1 = 0;
var disable2 = 0;
var disable3 = 0;
var disable4 = 0;
var disable5 = 1;
var disable6 = 0;

function validate(type,input,errordisplay){
if(type == "blank1"){
if(!input.value.match(re)){
errordisplay.innerHTML = '<span style="color:#FF0000;">Invalid Input</span>';
disable1 = 0;
}
else {
disable1 = 1;
errordisplay.innerHTML = '<span style="color:#006600;">Valid Input</span>'}}

if(type == "blank2"){
if(!input.value.match(re)){
errordisplay.innerHTML = '<span style="color:#FF0000;">Invalid Input</span>';
disable2 = 0;
}
else {
disable2 = 1;
errordisplay.innerHTML = '<span style="color:#006600;">Valid Input</span>'}}

if(type == "blank3"){
if(!input.value.match(re)){
errordisplay.innerHTML = '<span style="color:#FF0000;">Invalid Input</span>';
disable3 = 0;
}
else {
disable3 = 1;
errordisplay.innerHTML = '<span style="color:#006600;">Valid Input</span>'}}



if (type == "email"){
check=/^\w+[\+\.\w-]*@([\w-]+\.)*\w+[\w-]*\.([a-z]{2,4}|\d+)$/i
if(! check.test(input.value)){
errordisplay.innerHTML = '<span style="color:#FF0000;">Invalid Input</span>';
disable4 = 0;
}
else {
disable4 = 1;
errordisplay.innerHTML = '<span style="color:#006600;">Valid Input</span>'}}

if(type == "confirmemail"){
if(input.value.toLowerCase() != document.getElementById("contact_form").email.value.toLowerCase())
{errordisplay.innerHTML = '<span style="color:#FF0000;">Invalid Input</span>'
disable6 = 0;}
else {
disable6 = 1;
errordisplay.innerHTML = '<span style="color:#006600;">Valid Input</span>'}}}

function checksubmitbutton(){
if(disable1 == 1 && disable2 == 1 && disable3 == 1 && disable4 == 1 && disable5 == 1 && disable6 == 1){
document.getElementById('contact_form').submit.disabled=false;
setTimeout('checksubmitbutton()',1000);}
else {
document.getElementById('contact_form').submit.disabled=true;}
setTimeout('checksubmitbutton()',1000);
}

Code (markup):

 

Which has an indicated error in validate.js: 'fuction'. Perhaps you could fix that first.