Hm, I experience the same problem with a symbol, but it doesn't bother me too much because I rarely use it. xD But, I remember when I could use it, I remember accidentally pressing another key along with it between the space bar and the arrow keys, then I could no longer use it. So, maybe mess around with the suggested keys until it (hopefully) lets you use those symbols...? I dunno, this seems a bit dumb, but hey, this happened to me, and it might work. >.> Good luck.