I have been using a Nexus S since 3 months, and it has this annoying issue of being suddenly unable to send text messages for days together. I first thought it was my carrier, so I switched today, and the problem persists. Googling brings up a few stuff, which I tried (dial *#*#4636#*#* and manually set a SMSC code), but to no avail. The code simply vanishes everytime I get out of that screen. Please help!