Everytime I add a new view port to my drawing set, it blanks out one that I have previously already set up.  I then, cannot edit the blank one and have to delete it and re-add a new viewport for that drawing which leads to it blanking out a new different view port and so on and so on.  Is there a viewport limit or setting I have mis-set up? 

Yes, a setting that controls maximum visible viewports-
MAXACTVP
 
crank 'er up higher :)

Thank you, thank you!