[Vimperator] Question about e.g. Australian Open site

[guivho]

Hi,

I have a number of tabs open, among which http://www.australianopen.com/en_AU/index.html

When I switch to that tab with gt, I can not switch to the next tab: vimperator does not react.
However, when I hit <C-Q><Esc>gt it does work (So temporarily entering passthrough mode).
 
It's not really clear to me why this is the case, nor whether there is a better way to achieve this.

TIA for any help / explanation.

Guido