[ChazC]

I'm on CPTK so I don't have the overall option for Auto Input only. But so far, it hasn't made any difference with some tracks in Input Only - interesting information though, thanks.

Just out of curiosity I fired up the worst session I experience the lock ups on (it's worst while editing MIDI but even just getting the transport or record enable buttons etc. to respond promptly is a problem in this session) and the mouse pointer is fully responsive & moveable while Protools is frozen so I'm not sure if that points to a Protools GUI redrawing issue rather than a graphics card incompatability?

{edit to add}My buffer settings make no difference either, it locks up from 64 thru 1024 regardless. Pretty miffed because I had 9.0.3 rock solid - I'm rolling back the spare studio PC to 9.0.3 as this freezing issue is really starting to become unworkable in certain sessions - it makes MIDI editing nigh on impossible.