[davepl]

No expert on brakes, but the slider valve that's in the middle of the prop valve can be forced to one end, locking out one circuit, making it impossible to bleed. Does it sound like that?

There's a way to remove the brake light sender and hold it in place while you bleed, or something to that effect, if it happens to you. Search the forums or others may be by soon with more info if you think that might be the case...