I had the same problem with my new Camelback magic that I bought two weeks ago. I actually had to ask my bf to open it because I was closed so tight and I never did close it that tight. I think it has to do somethign with rubber on the lid, it sort of sucks to the bladder oppening if you know what I mean. Putting it under running water was a good suggestion, maybe the rubber has to soften a bit.