Audio Interface Recognized, but No Input Signal

This is December.  Back in June I ordered a pre-sonus audio interface, think pad laptop, Sonar X1 Studio, and various other recording equipment.  I had little to no trouble assembling the pieces and working out the first kinks.  By August I had successfully recorded an EP.  Since then I have recorded much more.

The point is - I'm getting pretty comfortable with this software and equipment.  I feel like I 'know my hardware/software' to a certain extent.  I have had NO problems thus far that I have not known what I did or how to fix.  OK.

A few weeks ago I opened my software and set up my equipment.  Basic check before recording begins.  Sound goes into mic.  Sound goes through very simple tube pre-amp, which powers the mic.  Sound goes into audio interface. Sound goes through my usb port into my computer.  Sound reaches software.

Recording light is on (standby, basically); volume levels normal on my interface and preamp; interface recognized by software; everything is just as it is every time I record.  Only now, there is no input signal.  At all.

I've switched mics, restarted the computer and software - I even re-installed Sonar X1 Studio. It may be some simple thing that I am forgetting - and I actually hope so - but the fact that I have changed nothing and it has all of the sudden not picked up my input signal, that makes me scratch my head.

The problem is that I am scheduled to cut a record with a friend back home over Christmas break - AH! Haha so any advice you guys might have would be awesome.  It's a long post, I know, but I wanted to make sure everything was properly communicated.

Thanks

reinstalling is almost always a waste of time.  99% of the time it's not because of corrupt software.

did you double check your INPUT on the track to make sure it's set to the same one that you've plugged your mic/preamp into?

is the track armed?

have you tried a different input on the soundcard in case the hardware has gone bad?

what kind of mic?  condensor?  is phantom power on?

have you tried bypassing your tube preamp and going directly into a mic pre on the presonus?

Daveny ?? Windows mixer-- That's only for on board and does not effect an audio interface. At least with mine it doesn't. 

You never mentioned if the track you armed level meter is showing input. If not then you have not chosen the correct input from the list. 
Double check as most interfaces  have a somewhat confusing list. 

Mike  1 Left = input 1 
Mike  1 Right =input 2 
etc. 

That's only for on board and does not effect an audio interface. At least with mine it doesn't. 

It does on my Delta44.