My Beats X just died too.
They were working fine until a few days ago, and then nothing - no lights, no sounds, nothing.
In the last few days I've tried every method to reset (inc holding down reset for over 2 minutes..), nothing helped. Now the white light is on and won't turn off.
I'm on a 4 week business trip in Asia, so no chance to take them back or get them fixed.
I tried to find when the firmware updates were pushed through to see if it was an update that killed them..
There must be a firmware update that can fix this, or a way to back-date the firmware to the previous version that worked..
Does anyone know if this is possible?