Sound Cutting Out

[TommyTenToes]

Ok, I've got Vista and a Creative SoundBlaster X-Fi Xtreme Music... all drivers etc are up to date. When I'm playing music through iTunes, Spotify etc, it works fine, but when I open certain applications, mainly games, the sound output starts to falter and then cuts out. Every so often it will kick in again but usually fail again fairly soon after.

By games I mean anything from Football Manager to Minesweeper/Solitaire.

Any ideas what this could be caused by as it's starting to get very annoying!

Thanks