Visual input levels but no audio

[Burton...]

I'm not sure if this a 5.1 issue.
I've been using 5.1 for six years or so, much of the time without any problems.
I recently reseated the main cards of a mix plus system to fit a serial midi port.
I rebooted protools and now have track 1+2 with constant input levels but no audio.
Does anybody have any ideas what is happening, I have run a digi test, all seems to be
ok with the test but still the same 2 green lines of input level but audio.

Exasperated...

[RobMacki]

Is this an 888|24?
When you record arm do you hear audio?
I had an issue with an 888|24 with spontaneous input signal. Digi dealt with it. I slipped under the wrnty.
I'd also check my I/O settings just to dbl check too.

[mfranken]

This might be it:

From memory if your clock source is set to S/PDIF (session setup) and there is no digital signal present you will see levels but no hear any output.

Cheers Mark