QuickTime Player error

I wrote the following script wich merges an audio file and a qt file into one file:

tell application “QuickTime Player”
activate

try
	if not (exists movie 1) then error "No movies are open."
	
	stop every movie
	
	if not (exists movie 2) then ¬
		error "This script merges the front movie into the movie behind it." & ¬
			return & return & "Only one movie is open."
	
	-- CHECK FOR THE CORRECT VERSION
	set QT_version to (QuickTime version as string)
	set player_version to (version as string)
	if (QT_version is less than "5.0") or ¬
		(player_version is less than "5.0") then
		error "This script requires QuickTime 5.0 or greater." & ¬
			return & return & ¬
			"Current QuickTime Version: " & QT_version & return & ¬
			"Current QuickTime Player Version: " & player_version
	end if
	
	-- CHECK FOR QUICKTIME PRO
	if QuickTime Pro installed is false then
		set the target_URL to "http://www.apple.com/quicktime/download/"
		display dialog "This script requires QuickTime Pro." & return & return & ¬
			"If this computer is currently connected to the Internet, " & ¬
			"click the “Upgrade” button to visit the QuickTime Website at:" & ¬
			return & return & target_URL buttons {"Upgrade", "Cancel"} default button 2
		ignoring application responses
			tell application "Finder"
				open location target_URL
			end tell
		end ignoring
		error number -128
	end if
	
	tell movie 1
		rewind
		select all
		copy
		select none
	end tell
	close movie 1 saving no
	tell movie 1
		select none
		rewind
		select all
		add with scaled
		select none
		rewind
		select at 0 to 0
	end tell
on error error_message number error_number
	if the error_number is not -128 then
		beep
		display dialog error_message buttons {"Cancel"} default button 1
	end if
end try

end tell

tell application “QuickTime Player”
activate
save movie 1 in file “testfinal.mov” as self contained
close movie “testfinal.mov” saving no
end tell

The script runs on my computer, However, it displays the following error:

execution error: QuickTime Player got an error: Network file permission error. (-5000)

when I tried to run it on another computer.