I use my 13" MBP in bed on my lap while on top of a large hard cover book. After I use the laptop for about 20 minutes or more, I lift up the computer and the blanket is wet. Under the book is wet and around the lap top is wet. Is this condensation building up? The air temperature in my room isn't even that cold. This is really strange but condensation is the only thing I can think of. The problem doesn't seem to occur on a desk or table. It only happens when I use the laptop on my blanket. I'm not sure the fabric of the blanket but it kind of feels like a polyester.