So this is a strange one. I performed the first sensor clean on my D800 in all of the 5 years that I have owned it (yes I know.....). The crud on the sensor wasn't actually that bad, and on checking using the usual shooting at the sky at f16 it appeared from the Jpegs that 80% of the dust had disappeared. However, when I tried opening the Raw file to my horror and near collapse caused by an exponential increase in my heart rate, the Raw files were corrupted. Thinking this surely must be an SD/Compact card flash thing, I swapped these out and took more shots. However, all Raw files were apparently corrupted.
After a sit down, a cup of tea (I'm English obviously) and after wiping the tears from the eyes I decided to reinstall the Firmware and.... voila.. is working and recording Raw without any corruption.
Has anyone suffered anything like this before? Really quite strange as I was rather gentle with the cleaning process.