Once this happens, it stays like that until a system restart. If I quit the game and restarts the launcher (Play/Options/Data files/...), its music has the same problem. So has the music/sound of any other game I launch (for example R.U.S.E.).
DXDiag: http://csharp.pastebin.com/dddKMyrG
Does anyone else knows something about that kind of problem? I'm not entirely sure it's Fallout: New Vegas but I didn't seem to get this trouble anywhere else. I do get the same phenomenon from playing music with Winamp in DirectSound though, but not that badly and it doesn't influence other games if I launch them after (like the launcher of FNV as mentioned above), and it does work smoothly with WaveOut so I believe that is just a problem with Winamp DirectSound module - happens to other people too. But then again it also feels a little bit like a problem with DirectSound.
The game is from Steam and has the latest patch, the drivers are up-to-date and so on. Windows 7 x64 and the sound card is ASUS XonarD1.
Tried the game support several times, but they don't respond.
Any help would be greatly appreciated!