First thing, don't call randomize after a wait action on start of layout. Move it to event 2 instead, as you have no way of knowing for certain if the Ajax request will complete in .0001 seconds or 10 seconds.
What is your default array size? From what I can see, your randomize loop will delete all your array x indexes after being run once. The second time, the loop will run for 0 to -1, since your array width will be 0 by then.