Hmm...
First: update your game to the latest version. Try the BIS site if the other site is too slow, I didn't have any problems downloading from there. There is absolutely no reason to stay in an older version. I think your script doesn't need a new version, but I don't know for sure about your version so update now. You'll need the updated version when you start making use of newer features in the scripting language. Make sure your friend updates too.
;D
You are not telling how you are calling the script... are you calling it at all?
Has to be like
[unit,vehicle] exec "script.sqs"
for example in object's initialization field or in a init.sqs file.
Make sure the mission editor is in advanced mode.
I don't see any errors in the script itself. I tried the script and it works just perfectly.
I called it from the player's initialization field like this:
[this,jeep] exec "script.sqs"
where jeep is of course the name of the vehicle that is "trapped".