A couple days ago I was using nudge on midi notes in PRV without issue.
 
Now if I nudge left (1, 2, or 3) the selected note disappears, as if it's been nudged a long way.  Ctrl-Z brings the note back.  Nudge right (1, 2, or 3) work as expected.  I've tried changing the nudge settings.  I've used the process menu to invoke nudge instead of the num pad.  It just doesn't work.  I've closed the project.  Rebooted.  Etc.
 
Ideas?
 
Thanks
 

I just tested mine - works as you said yours did before the problem.
 
The only thing I can think of right now is take a look at Edit...Preferences...Customization...Nudge.  The "Follow Snap Settings" in mine are un-checked. Just to be complete, my settings are:
Absolute Time
Nudge1: 10 milliseconds
Nudge2: 1 frame
Nudge3: 2 frames

So I created a new project, added a synth, recorded some midi, went to PRV...
 
Nudge works fine.
 
Open my other project.  Nudge left doesn't work.  Nudge right is fine.
 
Apparently nudge preference settings are global to all projects, cuz the new project had all the latest settings from my problem child project.
 
I guess I can export/import all my tracks to a new project and see if the problem persists.  Yuk...
 
Cheers
 

Resolved!
 
The midi clip must be selected in Tracks view for my left nudge commands to work in PRV...
 
Kinda weird but there it is.
 
Cheers