Don't dig it up!

Clematis are subject to a disease called clematis wilt that can cause stems to die back unexpectedly. Your plant may or may not be going through that. Also, the clematis stems are very brittle -- so they're easy to break accidentally -- and if that happens, naturally that'll cause them to wilt as well.

Many times the plant will come back from either insult. Cut out the dead vine and throw it away, and then take a deep breath and let the plant have a chance to recover! Even if **all** the stems die, the plant may still come back from the roots. Sometimes they'll even do that more than a year later -- so patience pays off.

Good luck!

I second what Anazindirt said. Also look for damage at the base of the wilted stem. Slugs, rabbits, sudden winds could all cause damage to the stem that has caused wilting. You could also add some organic mulch on the ground around your clematis (but not against the stems) to help maintain even moisture. When you water, first check that it needs it (you want to aim for lightly damp, not dry and not saturated a few inches down), and then if it does, give it long and slow water such as from a dripping hose for a while rather than a quick spray from a hose.

Great advice you guys!! Thanks for giving me hope! I'll keep my fingers crossed, and take deep breath!