I am so upset about one of my clemats....

It was growing realy well with all new buds, then all of a sudden, one side on my plant just wilted with drooping leaves and buds. I saw no bugs, and we have had plenty of rain. It is as if, someone cut the vine near the bottom, and half of my plant just wilted and and is dieing. BUt the vine is perfectly in tack all the way down to the grown. Does anyone have any idea of what it could be? I live in new England, the weather here has been in the 60's and 70's all week. It is in a state of active growth. I saw no bugs on the plant itself and there has been no frost. Could it be possible that an insect is eating its roots such as a grub? Could it be in the roots and what would you water your plant with to kill an insect eating the roots if so?

Please, anyone help me before I may loose the rest of my beautiful plant..:-)

Thanks so much