The last few OS's that I've had, I've experienced this problem.
I'll be listening to music (through headphones) and try to unlock the phone. The phone will stay at the screen that pops up when you first try to unlock it with the blue at the bottom fading into black at the top. Then it will stay stuck on this screen. The music will continue to play but nothing I do will make the screen go away. Once the song finishes, the next song will not play. The only remedy is to do a battery pull.
I've experienced this with .103, .99, .90 and maybe even before, but at this point, I don't even remember anymore. Has anyone else noticed this problem also?