ThreatLevelMidnight

I recently changed my battery on my Legacy. Everything was fine for a while after that, then one day I went to start it and when I turned the key, I lost all power to the car. I looked under the hood and as soon as I touched the positive terminal, power came back, it started up just fine, and I got home. The next day when I went to leave, the same ting happened. Again, I basically tapped the positive terminal and power came back, but this time I figured I should take some extra time and make sure this wasn't going to keep happening. Upon closer inspection, the connections were a little loose, so I tightened them up. All good, right? I thought so, but then when I started it, the ABS, brake, and VDC light all came on and stayed on. I looked up what could cause this and couldn't really find much. Some of the troubleshooting I saw was to disconnect the battery, then connect it again, but that didn't work. Has anyone experienced this or have any ideas on what the cause could be?