Moisture on insulaltion in basement

This is the first summer I have condensation on my insulation in my basement. I can't figure out how this happened. I have a de-humidifier running and I have vents in the basement. I never keep the air conditioning too high. Anyways, I am going to replace the wet insulation, but how can I prevent this from happening again? Any advice would be appreciated. Thanks.

Well if anyone is interested in knowing how I fixed the problem, I just ran my dehumidifier 24 hours a day (usually I turn it off at night). I also put the a/c on about 75 degrees so the basement wouldn't be so cold...plus shut the basement vents (left them just slightly open). This seems to have done the trick.