Help No Texting After ICS Upgrade


My text messaging ability disappeared after I upgraded to ICS. All I get is the message, "Unfortunately, Messaging has stopped." with the word OK below that. Has anyone else had this problem? If so, how did you solve it?

Also, in trying to see what caused this and went wrong I went to Settings, Wi-Fi, More, and Mobile networks. Everything looked fine until I then clicked on Access Point Names and saw Cingular followed by a number. Since my provider is AT&T and not Cingular, I thought this was the mistake and chose Reset to Default from the menu in the upper right corner thinking AT&T would come up for me to select. Instead, Cingular ___ went away and nothing else came up so the screen is empty. Now, I don't even recall the number which followed the word Cingular. Is there anyone who could follow the same path and let me know what I should enter?

I'd be very grateful for any help.