Thanks for the suggestions. You are right, things will definitely get interesting now...I need to go find my multi-meter pronto!
I believe they are 9007 off the top of my head. I had wondered about a ground issue, but don't the high / low beams share a common ground? I also wondered about checking the bulb socket, I didn't do that when I swapped the bulbs out.
I had a similar problem years ago with a 2000 Cherokee that I gave up and took to a Jeep shop and it ended up being a short BEHIND the fuse panel. I'm really hoping that's not the case as I don't want to get into that myself.
That being said, I do have a couple other wierd electrical issues to look into (the two cigarette lighter plugs flanking the stereo are dead, and the stock stereo doesn't retain the settings when you turn the truck off). I really hope they aren't all part of a bigger issue.