I'm running XFCE 4.12 on top of Gentoo with a 4.2.0 kernel. My PlayPause button on my keyboard used to work as a global hotkey for VLC. Now VLC won't even recognize the key. It does see "Alt + Media Play Pause" but not the key alone.

Is there a way to see if and what program might be capturing that key?

When I run xdotool key "XF86LogGrabInfo" the tail /var/log/Xorg.0.log file reads

[ 10138.690] (II) Printing all currently active device grabs: [ 10138.690] (II) End list of active device grabs