I remember this EXACT symptom set occuring not even three months ago..
it was, indeed, a fuse, and it was a fuse that wasn't expected.
I have no cd, or books with me (out of town) but you could search.. I responded to the post with the correct fuse number. Of the top of my head I wanna say it was fuse 20-something (though which one, or if I am off, I don't know).
The BOO switch is out, since your third brake works.
Have you tried VERIFYING that the bulbs are good? There is a seperate element for the turn signals, so turn signal operation doesn't cut itt. Simply looking at it doesn't work either. a bulb can be bad and the filament still intact.
I would use a voltmeter to measure voltage at the brake light harness while the brakes are pressed.
you have voltage, its the bulbs. If you don't, then work from there.
Ray