Loop command isn't looping

[TheTerrarianBrony]

I've never had a problem with the loop command before, but can someone tell me if there's something wrong here?

a::
loop
{
send x
random, sv, 3200, 4000
sleep, sv
send +{space}
}
return

[mikeyww]

It loops for me. Is this your entire script? What happens when you run it in Notepad, and press a to trigger it?