Hi there Guest,
Happy to hear from you! My guess is that there's a compatibility problem with the material your sleeves are made of (probably PVC) and the chemistry of your prints. Also, high humidity can cause the surface of the print to stick to the inside of the sleeve. I live in TN and humidity is something we have lots of.

What I do is use non-PVC sleeves (known as archival preservers) with ink jet prints (and also to store film negatives in) and have not had any problems. These sleeves are designed to fit in a notebook and come in a vast assortment of pocket sizes (suitable for 4x6, 8x10, etc.). You can buy them in packets of 25 or 100 sleeves from area photo shops. If you can't find them in your area, you can order them easily online.
Hope this helps you!
Deb