I had a problem with mine this morning :/ It was stuck at the bootscreen. I have tried a hard reboot, took the battery out and back in, tried to reboot from the Recovery mode but nothing :/
I had to reset to factory through the Recovery mode and then it booted normally but I lost all the music in the internal memory...
Is it a known problem ?
I think I had this problem or it could have been that my DX 50 fail to boot because low battery anyway u can avoid this by putting all your music externally, that's how I do it.