I tend to get this problem when I unplug the phone from the pc before unmounting it. (Right clicking the icon on bottom right and s choosing to...
Sms works fine for me, mms... sending pictures is fine, but when it comes to large texts, sending always fails.
I'm really diggin the look of this... WHat set-up are you using?
I'm new to the forums, but not to android. Just got myself a SGSIII from metroPCS and looking to get into a new community :)