Choose from list inside Address Book tell block locks MacBook

I have a puzzling situation.
The below code works. But if I remove lines 3 and 9, putting it all inside a single tell block, my MacBook (with OS10.5.8) locks up. I can’t figure out why.
Does anyone have any thoughts?

tell application "Address Book"
	set groupList to name of groups
end tell -- ************************Line 3

copy "ALL" to beginning of groupList
set uiSelections to choose from list groupList default items {"ALL"} with multiple selections allowed 

tell application "Address Book" -- *********************Line 9
	if uiSelections = false then
		return item 1 of uiSelections
	end if
end tell



read the paragraph about AppleScript Security Changes of AppleScript Release Notes for Mac OS X v10.6

Probably this is the cause

I’m not running 10.6, so I’m not sure if the Security Changes apply.

However, its good to know