I am not able to send any text message. It gives me the red X and says "Protocol error". I can recieve them. I can also send/recieve emails. I reboot my device and even tried a battery pull. I checked my service number and TCP settings also.

What gives??
Anybody have any ideas why.

Wirelessly posted (8700g: BlackBerry8800/4.2.1 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

At Options > SMS, do you have Network to Send Over set as GSM?

EDIT--should have said GSM.

I'd make sure that you're provisioned properly with at&t. I can't count the nuumber of times we have had to call them for SMS provisioning issues.

No, it's set to gsm. The only two other options are gprs and gprs preferred.

I edited my post, mis-typed. Should say GSM. Do what Takeshi said, call the carrier. It can drop from the service at times, posted on the board here a few occassions.

Got it resolved. I had the wrong service number in my phone. Now its working.
It's still weird because I used the other service center number since last Friday.