[Zxion]

This happened to me and I noticed it was because I had all of the sound in the F3 menu turned off. I don't know if you have yours set that way as well, but if you do try to turn it back on and walk around to get the walking noise to activate. After that, check the volume window, it should be listed again. Also, even if you don't hear any sound after walking, be sure to check it because it might be muted within the volume control window itself. Hope it helps!