Cyccommute, you're right that the guard was funneling a lot more water onto that side of the BB. Like I said, I'm going to ride for the rest of the rainy season with nothing mounted through the BB so I can see if the problem was related to that installation.

In the mean while, I'm looking at this kit as a possible solution.
http://store.velo-orange.com/index.p...uard-kits.html