Windows Media Encoder 9 from rapps refuses to install due to missing qcap.dll, requires DirectX Media 8.1 or higher

ros 0.4.12-RC-55-g3a6cb85 gcc dbg lin is affected and all the release tests down to ros 0.4.0 always failed with the very same MessageBox whenever I tried to install
"Windows Media Encoder 9"

err:(win32ss/user/user32/windows/messagebox.c:1048) MessageBox: L"This application requires DirectX Media 8.1 or higher. Please install the DirectX Media 8.1 or greater run-time from www.microsoft.com/directx before running this Setup."

There is no other interesting logging, beside that one.

The app was added to rapps in SVN r47826

So I thought, ok, let's retry after installing "DirectX 9.29 Runtime June2010" from rapps beforehand, but that did not help either. Same error.

Is there some trick/workaround known to get this to install? I mean, why is it in rapps if it won't install?