Address Book Plug-Ins: Age

I have an Address Book plug-in that showed the age of a person when clicked on the "Birthday" label. Since installing Snow Leopard this stopped working. The script is still where it's supposed to be, and other scripts in the "Address Book Plug-Ins" folder still work. Any idea why the age script stopped working, and how I can make it work again?
The script – I don't remember where I found it – now looks like this:

{quote}
<pre>
(* This script adds a popup to birthday field that shows the persons age *)
using terms from application "Address Book"
on calculateAge(bdate)
set age to ((year of (current date)) - 1 - (year of bdate))
if (month of (current date) > (month of bdate)) then
set age to age + 1
else if (month of (current date) = (month of bdate)) then
if (day of (current date) ≥ (day of bdate)) then
set age to age + 1
end if
end if
return age
end calculateAge

on action property
return "birth date"
end action property

on action title for p with e
set userAge to calculateAge(e)
return (name of p & " is " & (userAge as string)) & " years old"
end action title

on should enable action for p with e
return true
end should enable action

on perform action for p with e
set userAge to calculateAge(e)
display dialog (name of p & " is " & (userAge as string)) ¬
& " years old"
end perform action
end using terms from
</pre>
{quote}