Hissing on export / export dialogue is a mess

I am running Cubase 7.0.2.2107 on a Mac Desktop under Snow Leopard (10.8.2)

Audio exports from Cubase 7 have an audible hiss laid over them. This happens when I export individual channels or a full mix, AIFF or WAV mono or stereo or stereo split, at all different sample rates.

It DOES NOT happen when I export as an MP3.

One notable thing is that the the display of the export dialogue window is all messed up on screen, so it is VERY HARD to see what the settings actually are. Possibly I have some other feature switched on but the text and boxes are overlaid on each other in such a way as to render this very hard to see. I attach a screenshot.

Can anyone help?
Screen Shot 2013-02-23 at 11.19.07.png

OK, stupid error. It was just a matter of resizing the dialogue box, which I did not realise you could do. Turns out everything was being exported at 8bit which explains the horrible artefacts. The bit depth drop-down menu is pretty much entirely hidden when the box is sized too small. Ooops.