Thunderbird 7 on Ubuntu Oneiric

[Mihamina Rakotomandimby]

Hi all,

On Ubuntu Oneiric, the thunderbird 7 icons are those black ones:
http://www.zimagez.com/zimage/screenshot-09212011-084756am.php

I expect them to be the old ones, more looking like GTK icons.
In the settings (tools, addons, apprearance) Default 7.0 should be the 
ones I want. But in fact, they are those gray ones.

Is this because of a third party Ubuntu package overriding the apearance?
How to get the default buttons back?

-- 
RMA.