I bought a Nexus S from Best Buy about 10 days ago, and saw this issue a few hours after turning the phone on for the first time. It didn't happen again until about two days ago. And boy was it bad. Yes, was on 3G at the time, and the signal level was not very high. I have not once seen in when I'm using WiFi. My phone is 11.07, Gingerbread 2.3.4.