Native Asio freezes with Asus Xonar DX

Hi, I am running Windows 8.1 64-bit with the 64-bit version of Renoise 3.0 beta 6 (though the problem existed in 2.8 as well).
My soundcard is an Asus Xonar DX which supports native Asio, but I can’t seem to get it to work with Renoise.
The problem is that when I select the Asus Asio driver, the sound freezes after a few seconds of playback (and is also much louder). Then I have to reset it in order for it to stop.
When I open the Asio control panel from Renoise, the settings are locked to 10 ms latency and 16 bit resolution, similar to this thread.

ASIO4ALL seems to work fine though, but it would be nice to use ‘proper’ Asio now that my card should support it. I’m using it with the Unified Asus drivers without any modifications.
Anyone had any luck getting Asio to work with this card and a 64-bit installation?