I just joined this forum and saw your post. I had something similar happen with another brand of headphones and I actually got them replaced. Unfortunately it didn't fix the problem. What I found was that the headphone port on the phone had gotten a build-up of pocket lint inside it, which began to get compacted down with the headphone jack.
I guess this didn't allow the plug to line up properly with the pins for the extra controls.
I ended up using some a can of compressed air to blow the lint out and it has been working fine ever since.