as you can see, I registered in order to give you the reply :P
this is an OutLook (andNotOnly) BUG that MS has confirmed but does nothing to fix it (because it doesn't concern MS products)
see here:
http://support.microsoft.com/default...b;EN-US;821692
it should be fixed in next versions of FireFox probably. at the moment just get this fix (for another Mozilla valn this time)!
http://update.mozilla.org/extensions...nfo.php?id=154
or
http://dready.org/
0.7.2 is out to fix this, but the ONLY difference between 0.7.2 and 0.7.1 is this fix. so just get the fix :P