Bringing this old thread back to life just for an UPDATE on my problem in case anyone in the future uses this thread in a search:
I had already fixed the bad ground last summer but since then have just kept my lights on while driving so that my brake lights would also work. (The problem was my brake lights wouldn't work unless headlights were also turned on.)
I finally got around to taking my light switch housing apart to see what the wiring looks like. I found that the wire for the brake lights was 1)really loose almost falling off the terminal and 2) I believe it was actually connected to the wrong terminal. I crimped it a bit and put it securely on the correct terminal per diagram and now everything seems to work as it should.
It sure is a nice feeling to get something figured out/ fixed (even if it takes almost a year LOL
but that's the way it goes sometimes with job and kids and house and, and, and...)