brltty an usb-hub

[Dietmar Segbert]

Hello,
i use speakup and brltty with a optelec voyager 44 on grml linux.
If i plug in the voyager brailledisplay directly in into my netbook, all  
works well.
    If i plug in the brailledisplay into a usb-hub with a extra  
poweradapter, the brailledisplay works, but the keys of the voyager wil  
not work.
    What can i do, so that the brailledisplay works correctly.

Regards.

Dietmar