Hi guys,
I've finally realised that at least on my machine, there is a pretty serious conflict with Google Chrome (the web browser) and Cubase/Virus (Windows X64)
If I have Chrome running in the background I am usually unable to export in real-time without getting CPU overload errors - when I quit Chrome, the Virus exports much better, without causing errors.
Also, if chrome is running I tend to experience weird timing issues, like the virus latency increasing massively - without Chrome running in the background, these issues almost completely go away.
There appears to be some conflict with Chrome and Cubase/Virus on my machine, hopefully this will help someone else. I know you are supposed to have just audio stuff running on your DAW, but this is not always possible, and this conflict cost me loads of time and I have finally worked it out - now my production time is far more productive!
T Shark