toolbarbutton popup is transparent in firefox 4

Hi, in firefox 4, the toolbarbutton menu is transparent (see attached screenshot). When using a instead of a for torbutton-context-menu, the bug disappears. I tested firefox 3.0, 3.5 and 3.6 to check it did not break the menu (I did not test in thunderbird though).

Trac:
Username: arno

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