Droplet works on one machine but not another?

This is a small section of the droplet, I think it only needs this as when I removed the on open and replaced with choose file(S) it works and first prompt is 'Please enter the week number:"

The droplet works as a droplet on my imac 2009 but not on the 2010 or 2013?

They all have 10.9 installed. They are almost identical in configuration, even a reboot didn't get it working?

When you drop a file on the droplet the icon bounce and quits.

Why should this be the case.

If the rest of the script is the cause let me know but the fact the prompt won't come says it goes wrong as a droplet

property type_list : {"8BPS"}

property extension_list : {"psd"}

script o

property theseNames : {}

end script

property weekNumber : ""

on openthese_items

set weekNumber to ""

display dialog "Please enter the week number:" default answer weekNumber

set weekNumber to text returned of result

try

if weekNumber = "" then error

set weekNumber to weekNumber as number

on error

set thePrefix to "INVALID ENTRY! "

return

end try

repeat with this_item in these_items

process(this_item)

end repeat

end open