Audio mixdown corrupt

Hi, suddenly Audio Mixdown (in any WAV, MP3, WMA) are all corrupt. Tried with Windows Media Player and iTunes. Same.
I tried exporting a small section of the production. Same result.
Checked that I had the L-R markers the correct way (!) also.
Tested with just one track. Same.
Restarted the PC (Sony VAIO 64-bit Windows7). Same.

On iTunes the file simply does not start. on WMP it says WMP encountered a problem …
Checked that no ID3 tags.

What can this be?

Cubase 6


I had ‘Generic low latency ASIO driver’ selected in Devices. Changed to ‘ASIO DirectX Full Duplex driver’ and it worked.