Weird GTX 460 audio issue

New build, which includes an ASUS GTX 460. Connected to a Samsung LNT2342H 23" TV with a DVI-HDMI cable (no adapters/converters used).

All works great apart from an issue with the audio through the GTX 460 - every time it plays a sound for the first time in an application the screen goes blank for a few seconds and I get a "searching for signal" type message on the TV. Then it comes back on and all is well.

So for example, turn the computer on and as soon as it tries to play the Windows startup sound it happens (then Windows is happy), then load a game and it happens as soon as the audio starts (then the game is happy and it doesn't do it again until the machine is restarted), play an MP3 and it does it on the first one (then all MP3's will be fine until restart), then Firefox plays a Flash animation with audio and it does it (then Flash is fine until restart), and so on and so on....

Have tried both DVI ports on the card and both HDMI ports on the TV. Tried different drivers, tried looking for settings in the TV menu....tried pretty much everything I can think of, with no luck.

This is really annoying and I have no idea if it's the card, the TV or software. Any ideas? Thanks!