Your script runs fine for me on 10.9, however you don't seem to be targeting any application, it's not an issue, but you can find some weirdness when you run the script in the editor vs as an Application, script or service etc.
tell application "Finder"
display dialog "Hello, world!"
end tell
Try the above, see if that works - Finder should 'come to the front', you can 'compile' the script in the editor which should help confirm the syntax is correct. Are you using AppleScript Editor?
It's worth checking you are using the correct quote types (straight lines vs curly ones), especially when pasting from the web…
Bad
Good
There are a few tutorials around, see if they can help…
http://www.instructables.com/id/Simple-Applescript-Tutorial/
Macscripter seems to be helpful too
http://macscripter.net
P.S. 10.6.2 is a very old version, 10.6.8 is the later version (more stable) use software update to get that installed, it may fix some weird bugs that cause issues like this, run Software update several times until it stops giving you more fixes.