Good news.. i sussed it.
For some reason master {Asio driver) must have changed when i tried to export the mix on the fly rather than real-time export. Changed to Asio multimedia driver when it should have been Asio Hammerfull DSP driver!
Latency is back down to 6ms now
My hunch was right about the Asio at least.
Now i can get back to my Psy and beat the shit out of my Asio
Thanks Ben for helping
Still drops out of time on real-time mixdown though?