Media Keys Respond Twice in Windows Media Player

I have a Microsoft Digital Media Pro keyboard with play/pause, stop, skip
previus/forward keys for music. I installed the Intellitype software and
everything works fine for a while. Then at some point, a day or two later
this annoying behavior develops: the keys still work fine when Windows Media
Player has focus, on top of other windows, but when it is playing in the
background or minimized it responds twice to all of the key presses on the
media keys. If I skip previous or forward it will jump two tracks. If I press
the play/pause key, the playing music will hiccup and keep going because it
only momentarily pauses and then resumes. If no music is playing it will
begin to play and then immediately pause. The stop key still works as
expected, as there are no repercussions to pressing stop twice in succession.
I've had this behavior in XP Pro and Pro x64. I've uninstalled/reinstalled
the Intellitype software and it didn't do anything. Any ideas?