Is there anything other than the voltage regulator on the back of the alternator that can cause this? I replaced the VR about 6 months ago(last time the car was on the road), and I just noticed tonight, while running the car in the driveway, that the lights are flickering again. It's not bad, but it's noticible, moreso at idle than anything.

....if not then it is more than likely you VR again. I had the same problem. The VR brushes on my alt. were gone and the alt. wasnt charging correctly so I replaced the VR with out cleaning the comutator and it only lasted about 5 months. I just ended up replacing the whole alternator and it fixed the problem. Without cleaning and resurfaceing the comutator, the brushes on the VR wont last very long. My suggestion is to check the brushes again and more than likely they will be worn down to little stubs.