It sounds like what is called late damping-off to me. It is a fungus disease that attacks the plant at the soil line and while more common in seedlings it can also develop in older plants too - thus the "late" label - in damp weather.

The link below is to the FAQ here on damp-off and if you Google 'damping off photos' you'll find several photos of it that you can compare to your plants.

If the full plant isn't already infected the deep re-potting should snap them back into health.

Good luck.

Dave

Here is a link that might be useful: Damp-off FAQ

You might want to take a look at this somewhat-similar situation, particularly Carolyn's comments at the end.

Here is a link that might be useful: Tomato stem disease thread

Thanks, You are right, the images of damping off I found online look the same as my tomato plants. I could not find any info on how to save a plant, if I can save a plant. When I pulled them up to re-pot I removed as much of the soil as I could with out damaging roots. my guess is that the disease is in the soil since this did not occur until after they where put in the ground. should I remove the diseased part of the stem and try to root the upper stem? I have had nothing but trouble this year in my garden, what a shame. Thanks again for your help.

Peapod, I think you are right in thinking the disease may be in the soil. I had this happen in one of my shadier beds of tomatoes a few years ago. At the time I was using newspaper collars against cutworms which did not allow for good ventilation of the lower stem. Of the five plants in the bed, three continued to grow with some partial damage to the stem. Two of them did not make it. I cut them off and re-rooted in a milk jug, and then replanted in the same spots, and they both got the disease again a few weeks later, even with stems being open to the sun and air. I removed about 5-7 gallons of soil each where those two plants were located. I have since grown tomatoes in that same area, and had no problems the last two years. If you use mulch, pull it away from the stem itself so that area gets some air circulation.

I also had three okra plants get this disease, not sure why because they were in a sandy bed which was usually too dry. I noticed the ants there like you did, but in the end concluded that it was just damping off again.