Is armor rating the only factor that contributes to your overall armor rating? I just turned level 40, so bought some new gear. Basically the best stuff that was on the market, and my armor rating decreased dramatically. It is only about 1800 now, wheres as before it was nearly 4000!

I am pretty new to the game, only been playing a couple of days so maybe there is something obvious I am missing? I am a level 20 and have just gotten my slicing skill to 400/400 when I go to the trainer to purchase advanced slicing, nothing happens when I click. I tried logging in and out and still nothing. I even tried going back to the fleet and talking to the trainer there and still, nothing. any clue as to what is going on?