root system not big enough to support green growth so it wilts. when you cut it and put it directly in water it was able to draw it up.

Not a disease, a physical problem. The cells (cambium layer) that take up water are a thin layer under the bark, also very easy to injure.

I have a Violet Elizebeth that does this every year. She is over five now. I'd just toss her but a local Clematis grower brags on how great she is and has photos to back it up.

I'm going to dig her up and do a lot more soil prep and see if that is the problem. She was kinda shoved into clay with a post hole digger. If she doesn't perform next year after all this work then she is toast.

There are two schools of thought on "Wilt" One as BoS stated it's the immature rootsystem wilting off it's vines for preservation.Clematis want to survive and survival of their rootsystem is more important to them than their vines.
#2. It's a fungal disease
I am in concurrence with BoS..for I think it is a mechanism within the Clematis rootsystem to kill off its vines in order for the rootsystem to survive.That is why you'll hear so many of us advocate hard pruning the first couple of years so the plant has no other choice but to focus on growing its rootsystem and NOT its vines.A huge and Healthy rootsystem = a big glorious,healthy happy clematis that will reward you with her beauty year after year...Jeanne
ps..don't confuse "brown-out" with "wilt"...some clematis tend to "brown-out" during summer..it's just in their DNA or lack of sufficient watering..Clematis will risk the loss of leaves to preserve itself.Wilted vines turn black where as broken vines will brown and droopy vines (which are still green) will be revived with watering..were yours just droopy from lack of water?

I don't think mine were droopy from lack of water.
In fact, I have two of them, and they had huge root systems and were even growing out the bottom of the gallon pots they were in. I put each in its own 16" pot and they looked great. That was right until they started flowering... They started wilting one stem at a time. One has stopped and has 3 healthy stems left, the other keeps wilting and is down to 2 stems. I am worried that they may be rotting in their pots. I haven't watered them in a while, but when i poke my finger in the soil it always feels moist and cool to me.

That is how I always gage if my clematis needs watering..I put my finger down into the soil about 2 inches and if it feel dry I water otherwise I leave it alone..Even if clematis like their roots to stay moist..they need good drainage...Jeanne