Blank Waveforms - 11 not recording input, OSX

[Actionmusic]

10.8.4 11.0.3 2.26 Nehalem Mac

I've a VI heavy session mixed with audio, 80+ tracks.

Audio is routed correctly in PT, Microphone into Avid HD i/o, always audible in PT, meter moves so signal in - not intermittent mic or cable or external factor, I can always hear input and see the input on meters. Only one track in record, record a vocal take. Take is blank, and does not play back. No Waveform is visible during record as normal, or generated on pressing stop.

I cannot recreate this problem, it just appears randomly and doesn't go away with restart/reopen, but *may*at some point cure itself. Busy writer session today and it was a real PITA. Lots of recent NI VI's and others and everything else running live. Master bus with Ozone.

Turning off various plugs, masters, or changing buffers makes no difference. Trashing wfm in folder, again didn't help. It reminds me of the weirdness you might encounter on the most heavy TDM sessions, you just can't quite work out what is doing what.

This is more a request for other users to chip in, I'm happy to test certain scenarios to see if I can recreate.

In 10, same rig and external, working from a bounce down, all worked fine (apart from it wouldn't play live all the VI's as expected for processsing reasons)