trouble with Unicode sigs in Thunderbird

[Moustafa Mounir Elqabbany مصطفى مني ر القباني <elqabbany at sunnipath dot com>]

Assalamu alaikum.
كل عام و أنتم بخير
Previously, under Redhat 9 and Fedora Core 1, I would load a signature 
file automatically into Thunderbird and it displayed the Arabic fine.  
Now, when I do the same under a machine running Mandrake 9.1, the Arabic 
doesn't render properly, as you can see below.  I can still type Arabic 
in Thunderbird, as above.  Also, I am sure that the bytes in the 
signature are, in fact, correct, because I copied the signature file to 
sig.html and wrapped it in some html and then viewed it in Firebird, and 
it looks fine.  I'm not sure if the problem is a misconfiguration of 
Thunderbird or something else.

Also, I always use UTF-8 in everything, including the default encoding 
of my emails.

Your help is much appreciated.

--
Moustafa Mounir Elqabbany مصطفى منير القباني
(The above message uses Unicode (UTF-8) encoding.)

begin:vcard
fn;quoted-printable:Moustafa Mounir Elqabbany =D9=85=D8=B5=D8=B7=D9=81=D9=89 =D9=85=D9=86=D9=8A=
	=D8=B1 =D8=A7=D9=84=D9=82=D8=A8=D8=A7=D9=86=D9=8A
n:Elqabbany;Moustafa Mounir
email;internet:elqabbany at sunnipath dot com
tel;work:604.542.1830
tel;cell:604.710.6994
x-mozilla-html:TRUE
url:http://www.transparen.com
version:2.1
end:vcard