No Input Monitoring - Please help...

[rastus]

HI, Im running PT 9 , latest version etc on Mbox3. Never had any troubles previously but Ive lost all input monitoring. I know the hardware works because I can playback previously recorded tracks and I can record a new track - I just can't hear it either when record -enabled or when recording. GIven it plays and records as it should I know my I/O settings have to be correct. Is there something SO simple here Im missing?
I have tried this through headphones and studio monitors - same result.
I have tried the usual things like starting a new song from scratch, trying to work on an existing project, re-starting PT , rebooting computer....same result.
ANy help would be greatly appreciated,
cheers, rastus

[PD-John]

Maybe the Input Only Monitoring/Auto Input Monitoring setting has changed? Press Option + K to toggle.

If it's not this, try trashing Pro Tools Preferences.