why even
if x == 0 then do
if needs no do. you basicly made an infinite loop. let me restructure and fix it:
while rs.getInput("left") do -- you can pretty much always leave out == true.
x = x - 1
print (x.. " Till countdown")
sleep(60)
if x == 0 then -- here was a 'do' too much
rs.setOutput("right", true)
sleep(4)
rs.setOutput("right", false)
end
end
-- cut off 2 ends whch were too much
EDIT:
Also, i assume you defined x as local

(you don't need to, but it makes your code look better and its better coding style.
Also, you should always make sure your code you post it a valid extract or, better, post your entire code. if its a large chunk use
Gist or
pastebin. Gist has the advantage of allowing you to have multiple files on one URL