I think I figured it out. I took the whole ignition switch mechanism appart. There was a lot of gunk in where the copper contact points are. (probably from the dielectric grease) I inspected the switch last year, it looked good, but I didn't take it completely appart, like I did this time. (assumed the tumbler was the problem) Well, not only was there a bunch of gunk in it, but the contact points were pretty well worn. So, I cleaned it up, put it back together, and it works great, for now. Going to order a new ignition switch today. That should solve the problem for good.