Question
Problem:  (5)  5 year old snowball bushes planted side by side
         with plenty of space.  Have been doing absolutely
         wonderful until now.
         planted in Wisconsin

         Bushes grew beautifully
         Flowers were huge

         then all the leaves started wilting and
         tightening up.  Leaves stayed green and full
         of plumpness, no drying out.  Branches
         started to bend.

         Today I went out and was going to cut back as much]
         that would be needed to keep it healthy but, but          ended up cutting 2/3 of each bush down to only the woody parts was
         left.

      No bugs...nothing...
      I did notice when I cut a couple of the branches the
      inside circle was brown.  only one or two on each bush.
      The rest of the cuttings were all healthy looking.

         I have checked all disease photos and nothing is
      like what I have.
         Don't know if I should dig out or not.

      Note: Got plenty of water and was sheltered.  Late summer
         here in Wisconsin so the bugs are not out yet.  I
         pulled out a couple of roots to see if I would find  any bugs. NOPE!
       What can it be and what should I do?
Sandi

Answer
Sandi,

You did not mention leaf spots or holes from boring insects, so it seems that the problem your plants have is internal.  When fungi invade plants, they often block the movement of water and nutrients to the leaves.  The result is wilting and leaf drop.  Viburnum plants are susceptible to Botryosphaeria canker and dieback.  Since you noticed internal discoloration in the branches, that is consistent with this disease.

Unfortunately, there is no cure for Botryosphaeria canker.  Some growers have successfully pruned out the disease, but if it has reached the main crown, it is unlikely that this would be effective.  The main method of control is prevention by watering during dry periods and preventing injury.

For a little more information, please review these web sites.
http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/viburnum-diseases
http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2057.html

Sorry that I do not have better news.  It seems that the best option in this case is to remove the plant and replace it.  
-Jen