well i cant understand what you were saying about your script then as it would appear to do that, I did however try it on a channel with alot of people and it crashed due to string length, heres a script that should work all the time.

Code:
 
checkop {
  ;$1 is the name of the chan
  if ($me isop $1) {
    var %i = $line($1,0,1)
    while (%i > 0) {
      if ($line($1,%i,1) !isop $1) {
        mode $1 +o $line($1,%i,1)
      }
      dec %i
    }
  }
}