Happens to me occasionally, but only if I charge the tablet with the screen locked. Pretty sure it has something to do with Wi-Fi sleep settings, because it hasn't happened to me once since I disabled sleep as long as I don't plug it in. Seems like charging the device enables Wi-Fi sleep whether you change the settings or not, but I cannot confirm that. This has been the case on several different ROMs for me. I have gotten around it by turning WiFi sleep off, and powering down when charging, but I have not found a "real" solution.