konradh
I could hear myself in the mic and was getting a good level.  This all seems to fall apart when arming the track and recording.

Do you lose the input-monitoring as soon as you arm the track, or not until the transport starts running? Either way, I can't really think of a configuration/scenario that would cause this other than some kind of project corruption. Does this happen in a new project started from the Basic template? What if you output the vocal track direct to main/hardware outs instead of a Vocal or Master bus in the current project?
 
BTW, any particular reason you haven't moved on to CbB? It's light-years ahead of X1 in features and stability. And since it can be installed and run in parallel with SONAR, there isn't really a reason not to give it a whirl at least.

Check quick that the track itself is routed to something that hits the mains. The send to the reverb is making it all the way, but sounds like the actual track is not. Been a while to remember X1, but the CbB advice above would be worth checking out.

slartabartfast
I am confused about how you could hear the reverb on the vocal without hearing the vocal.

This can happen when reverb is used as insert effect with it's mix set fully on wet, or if vocal track's output (not send) goes directly to the reverb bus (and reverb's mix is full wet).

One of my tricks for trying to "find" a track that just won't allow itself to be heard no matter WTF I try is to look for something else (a track, bus or folder) that accidentally got solo'd. Basically go through my project and UNsolo everything.
 
I know, it's weird, you can hear it playback, so what I'm saying doesn't seem likely, but still, nothing else you've tried is working, right?
 
Maybe a bus? One hint is that your reverb send is working. It sounds like you're using a send bus to do your reverb, so there might be something over in Bus Land.
 
I believe this one dates back to the invention of the "solo" button on physical consoles. :-)
 
I'll second what brundlefly suggested about trying to route the track directly to the output. Put me in the camp who suspects routing or the wrong combination of mute(s) and solo(s) rather than a corrupted project.
 
Also, I don't monitor through a separate outboard mixer or via my interface. I use Sends and create Cue Mix buses, which lets me set up and store as many custom cue mixes as I wish without having to touch the main faders.
 
It requires a bit of sleuthing to find plug-ins that induce latency and therefore should be switched out while tracking, but Cakewalk (and yes, once you finish this session look into installing Cakewalk by BandLab) has a button that will bypass all of the effects in a project.

Thanks for the kind advice.  To clarify: the track records fine and plays back fine.  It is only the monitoring during record that is messed up.
 
I never use reverb as an insert on vocals: always a send to a reverb bus.
 
I'm sure I will figure it out.  Thanks for all your time responding.

TTo answer the question about how you can hear signals that are present both in a cue mixer and the interface. You need to be able to split the signal. 
There are many ways to set this up. 
Mike pre amps often have 2 outputs, one might be an XLR and the other a 1/4", so one gos to the interface the second to the mixer.
Many mixers have direct record output for each channel so thois is a easy one.
You can even double mike instruments, one mike records the other is just for the cue mixer. 
DI boxes always have 2 outputs so Bass or acoustic guitar is easy to splt.
I even use my Boss Tuner as it has 2 outputs. 
 
But getting back to Konrad, You should really figure the direct monitoring system of the V studio. I would think it should work and might be something very simple you've missed. 
There will always be latency when NOT using direct monitoring and the performance will be off time. 
I would never engage the input echo when recording audio. Even if it's only 7 ms it bugs me, 

Hello, Sock Monkey.
 
After I finish the problematic song, I will see what's up with the direct monitoring.  I have been through the directions and steps several times and can never tell that anything happens, but I will start over from scratch and go through it methodically.  After that, maybe we can discuss results.
 
Latency of any kind drives singers crazy.  I usually set ASIO buffering to the next-to-lowest number while recording (and the next-to-highest while mixing), but even with the low number, the latency is obvious.
 
Thanks for answering.