Looks like squash vine borers to me. Look at the base of the stem and see if you see any splits with saw-dust like pith coming out. If so they are eating the vines from the inside. If that's the case pitch the plant immediately.

I had the same problem. See my "Butternut squash not flowering" post. Unless your in the mountains, you probably have enough time to start another crop. SVB only attack once per year around Late May/Early June.

Thank you! I just checked. I didn't notice any dust or splitting. Could be wrong. I'll check out the thread you mentioned.

Look for a vine that has more leaves wilting when it gets really hot (it looks like maybe the leaves at the bottom of the picture are wilted more than the others). If you notice one, you may want to cut it off where it splits from the main stem(you might loose 1 pumpkin). Split it open vertically and look for grub-like worms. If you do have SVB's the plant is toast and you will want to get a new one started ASAP.

I looked at two of the wilting leaves but didn't see anything.

Phytophthora Root Rot

try this link out it will tell you all about root rot

Here is a link that might be useful: agri life extension

Thanks! Now to figure out how to save my vines, if possible.

No, East Tennessee.