MacBook Pro twisting!

I have an odd problem that is now beginning to alarm me. I bought an MBP 17" Aluminum Body model about a year ago, it is my main system and comes with me everywhere. Some time ago I notices that the lid, the top part with the screen, did not align properly with the base when it was closed. I thought it an anomaly and dismissed it, the difference was very small. But over the weeks this misalignment has been increasing and it is now off maybe a millimeter or so. If you look at the top of the laptop with the lid closed, the front left is skewed to the left, at the right back it is skewed forward and the top of the base at the right front is slightly exposed. In short, the top is twisting clockwise.

It has been a mild irritant to me and today someone mentioned that the batteries may be causing the problem. Is this possible? I had a battery in a previous laptop expand significantly very quickly, it was removable but was jammed, it took some considerable effort to remove without damaging the laptop, which we did, and Apple replaced it. This machine has a sealed battery and I am reluctant to remove the base, it has the three-year warranty.

Any suggestions?

Thanks - Lawrence