Yes, infact i do have AT&T , but the following seems too coincidental for
the facebook messenger app not be the culprit of this sms failure:
[EDIT]
+ (i send sms via the build it app)
+ ~ 10am sms working
+ ~ 11am updated facebook messenger app
+ ~ 4pm did not get sms from freind, tried sending out sms, not sending
+ ~ 4:30pm rebooted phone, sending sms not working
+ ~ 6pm sending sms not working
+ ~ 9pm received sms, send still not working
Tried sending sms at 10:30pm: no go

10:32pm uninstalled the new facebook messenger app.
10:35pm rebooted phone.
10:36pm tried sending sms, WORKED !
will try installing the facebook messenger app again, to see what happens.