I've had that happen to me on live 3 times now -- twice in the NT area and once in Leth Nurae. You can move and whatnot, just not see what you're doing. At first I thought I'd fallen through the world somehow, and did a /stuck yes to get to somewhere I *knew* I can't fall off of while moving, which didn't help but I do it anyway - who knows what trouble I could get into wandering around when I can't see
.
Relogging is what fixes it for me; I don't even need to quit the game, just log out and back in. Last time it happened I had to relog twice, oddly, but it eventually cleared.
Odd effect all told.