Shimano 105 Hollowtech II Bottom Bracket Cups
When your bottom bracket is toast, it's time for a new one. It's as simple as that. Shimano's 5700 series 105 BB will fit any of their Hollowtech II road cranks. This particular BB is for double cranks only. It won't work with triples. The threading is English.
I have this on a road bike so it should last longer than on a CX bike, and if it doesn't for the money it's really inexpensive to replace, it does feel very smooth in use. I think 105 is the sweet spot in the Shimano line, it lasts a very long time, it doesn't cost much, and the weight is reasonable.
External bottom brackets don't seem to last nearly a long as the old internal-style octalink and square taper units, but the good news is that the cost is pretty low too. The 105 level is as high as I'll go on my 'cx bikes, because these don't last more than one full 'cx season anyway.