Mine was changed after updating to 5.1.1 as well, however I'm using a Siri Proxy. I can confirm that with my proxy, it still works correctly on devices running 5.0.1. Anyone have any idea how to get the normal voice back? I tried shutting Siri off for 4 hours, like above, I tried changing the voice to other voices and changing it back. I also tried doing an iCloud backup, a few people on the Apple forums said that worked. I liked the normal voice much much better than the robotic sounding voice I have now. Any idea on how to get it back?