I'm having issues sending SMS's to certain USA numbers from my iPhone. I'm running 3.0 beta 5 but it was happening with Beta 4 also. I try to send an SMS to a USA based cell, but keep getting error messages. I've successfully send some from a different handset, so I'm thinking it's something to do with the iPhone.
I did update my carrier settings to make Tethering and MMS work - does anyone think this might be the problem?