According to many GSM Galaxy Neuxus users on Google Code, the newest 4.0.4 update is killing cellular signal after the phone has been in stand-by mode for more than 2 minutes. Further testing shows that if the minimum processor clock speed of the Samsung Galaxy Nexus is increased to 700MHz, or if there is a background app that puts a load on the processor, the problem does not occur. Users who flashed back to 4.0.2 report that the issue is not present after the downgrade is performed. If flashing back to 4.0.2 is not an option, a user over on XDA has reported that using a custom kernel with the Smart Reflex feature turned off solves the issue.When the phone enters standby, and nothing is using much CPU in the background, cellular signal is lost until phone is brought out of standby
The strange thing about this very serious issue is that it is not affecting all units. Only a specific batch of devices are experiencing the signal loss. Google is aware of the problem and hopefully a fix is on the way.