Running applescripts

I am trying to run a particular applescript from launch bar and everytime I run it I have to switch to Launchbar to see the applescript dialog box. I seem to be able to run other applescripts without any problem so it must be something particular to the script.

Here is simple script written along the same lines as the one that does not work:

on main()
   display dialog "Hello World"
end main
main()

I have Launchbar preferences set to "Run" applescripts. Does anyone have any ideas as to why this does not work?

I have tried running it using "alt + return" but it does not seem to make any difference.

Many thanks