[orca-list] Alt_F10 in Firefox refuses

[Milton <milton tomaatnet nl>]

Hi all,
I use Ubuntu 12.04 with Orca 3.4.2 in Unity 2D and Firefox 24.
With Alt_F10 I get acces to the menubar but arrow-down and arrow-up give 
no result, Orca stays mute. Aroow-left and arrow-right work as aspected. 
Do you notice this behaviour? What can be wrong here? How can I solve 
this. In Thunderbird 24 Alt_F10 and arrow-down work fine. Thank you in 
advance.
milton