When giving filenames as a parameter you need to have double-quotes around them if they contain spaces (added code highlighted in red). Also, you can improve the efficiency of that script by using $ifmatch in place of the second two instances of $script(%Count).
Code:
alias reload {
  var %Count = 1
  ; Unload all current scripts, except the current script
  while ( $script(%Count) != $null ) { 
  if ( [color:blue]$script(%Count)[/color] != $script ) { /unload -rs [color:red]$+(", [color:blue]$script(%Count)[/color], ")[/color] }
  inc %Count
  }
}

Spelling mistakes, grammatical errors, and stupid comments are intentional.