Vimperator. Unable to cycle through GUI elements in some dialog boxes

Question

I have a problem while using Vimperator. When I try to cycle through GUI elements (buttons, textboxes, etc.) in some Firefox dialog boxes and panes pressing the Tab button focus doesn't move to the next element but just follows to the viewport.

Here's the example illustrating the bug:

1. :open http://google.com;

2. :dia addbookmark;

3. The Add bookmark window appears and the focus is in the Tags textbox;

4. Pressing the Tab button doesn't move the focus to the next element but passes it to the viewport instead;

5. The Add Bookmark window becomes absolutely unreachable through keyboard keys.

How can I solve this issue and force focus to move to a next or previous element during cycling?

Thanks.

Debian GNU/Linux 5.0.6;

Firefox 3.6.9;

Vimperator 2.3.1.

Update

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Here's another one example:

1. :sb Bookmarks;

2. The Bookmarks pane appears and the focus is on the search box;

3. Pressing the Tab button doesn't move the focus to the bookmark list but passes it to the viewport;

4. The bookmark list becomes practically unreachable through keyboard keys.