I thought we were pretty positive that thsi is caused by using an emulators save function, not the games. Over long periods of time the game probably runs into huge amounts of errors relation to the system memory, and that causes the game to freak out, and just pick a texture set/file at random(then again, it could be the same every time, I haven't seen enough glitch textures to see if they're all the same in the same place). But since you said you didn't use it, I'd just assume the game glitched out, it loaded the wrong/right level, but the wrong/right textures. Do you have a picture of the chart position you started that dream at? (I know, fat chance, but you never know).
Try using the games save function, and then shutting the emulator down.
Also what Alundratix says is correct, the PSP/PS3 versions of the game are best, as they don't glitch out. (However the do freeze so often for me, that it's basically unplayable).