Chris,
If you're using the Arcsoft Alltel MMS cab, you'll need to change the server settings. It's very simple: open your text messages, select Pics/Video Options from the menu, and go to the Servers tab. Click on Alltel MMSC and it will bring up the server settings window.
Enter the following information:
Sever Name: Alltel MMSC
Gateway:[leave blank]
Port Number: 8080
Server Address:
http://mms-mt.alltel.net/servlets/mms
Connect Via: NETWORK
Send Limit: MAX
That should get your mms working. The text message problem sounds like a signal strength or Alltel transmission issue.