Hmm, thats an odd bug.
Having said that, I've had some weird similar bugs myself - I've experienced clicking the faces of a brush, only for it to select another brush fairly far away from the one I'm clicking, as though it was confused about which face I was selecting. The only way i've gotten around it is to do as Laged says and select it in the plan views, or try and select another face of the same brush in 3D view.
Just have to mark it up to BSP's strangeness I guess.
- Dag