Yes, I've had this happen a couple of times with a card installed. Pretty disconcerting the first time it happened. I cured it by shutting the player down and then restarting. Everything was there again when I accessed my music on the internal memory.
I find bugs are most likely to occur straight after I've had the player connected to the computer to transfer some music across. Something weird almost always happens. One common one is that when I try and access my new music the more sophisticated player crashes and I'm suddenly back listening to something that I'd listened to some time previously. But once it's settled down and been restarted a couple of times it works far more reliably.
My Westone 4Rs have arrived. Took about an hour for the sound to open out properly, especially the bass, but really enjoying them now. Finding them very neutral and natural sounding, but involving and transparent too. A good match with the DX100.
Is there any way to get rid of the fade in? It's driving me crazy.