CX-400 ear canal phones suddenly gone quiet

So guys, in November I picked up a set of Sennheiser CX-400 ear canal phones, and was very happy: well set up and sounded great.

Problem is, last week I was up skiing and during the week, both headphones went quiet. It sounds like the bass driver failed on first one ear, and then a couple of days later, on the other. Instead of producing a full sound, they give out tinny-sounding music at a hugely reduced volume.

A quick google gave similar symptoms here: http://www.head-fi.org/forums/f4/sennheiser-cx400-my-sad-experiences-short-review-309675/
So, it's a bit ick, but is it possible wax build-up is the problem? I've never had this problem with canal phones before, it seems unlikely to happen to both ears at the same time? And if it is a wax problem, what's the best course of action?

Its unlikely I over-powered them, I don't listen at loud volume, the only other possibilities I can think of are something to do with the altitude, or connection problems. Ideas anyone?