[villagetinker]

Since you are replacing the flooring, I would borrow a saw that will allow you to remove a small section of floor and take a look at what is below. Then a professional inspector could be contacted to see what is going on. Frank Dangelo (building inspector) is excellent and may be able to give you a hand in this matter. He normally advertises on this site.

I suspect you are correct, if the original home owner did not install the proper subflooring material you could be getting moisture from the concrete. Depending on the quality of the initial material a small amount of moisture could cause lots of problems. When I installed this type of flooring in our kitchen (up North), I took a sample and put it in water for over a week to see if there was any damage to the flooring material. I my case, no damage.

PS, I do have a suitable saw that I can lend you, or I could stop by, send me a PM if you would like to discuss further.