Battery goes flat

What can cause a power drain when the battery and alternator are brand new? I got the car in August 2012, and the battery and alternator were both bad, so I immediately replaced them. When the power drains started a few weeks into September, we tested the battery and it is perfectly fine so we know it's not faulty. Then we thought it was the power locks. They're busted and the driver side button is mashed in in the 'lock' position. We determined this was the issue to the power drain, so we took the fuse out and that kept the battery good for about two months. We thought we fixed it, til it'd die overnight again and again in November. We looked at other possible causes online and noticed the anti-theft device the previous owners added on was hooked up, but did nothing useful, so we took that out. It again seemed to have done the trick until now. Right now, it's going on a week of dying everyday. Fully charged during the day, then completely dead overnight, I make sure I am leaving nothing on when I get out of the car. We've checked to see if the trunk light was being left on, and no, it's working properly. I'm completely lost as to what it can be this time. I'm no car expert, but I know electrical problems can be ANYTHING and asking someone over the internet is probably impossible for someone to determine what the problem can be, but I'm hoping somebody will have other suggestions to try because I really need this issue fixed.