I have finally come up with the solution to my problem after spending hours upon hours this past week trying to get MMS working on 3.0.1. For those of you who haven't seen all the other threads, here is a quick explanation: If you have anything that modifies the AT&T carrier logo, uninstall that. This will fix the problem for the majority of users. However, it did not fix it for me. If you have done this or have never had the carrier logo installed then do this: 1) SSH into your phone and go to /private/var/mobile/Library 2) Right click and go to Properties of the folder 'Carrier Bundles' 3) Change the Owner from 'Root' to 'Mobile' 4) Go into the 'Carrier Bundles' folder and right click and go into the properties of 'ATT_US.bundle' 5) Change the owner to 'Mobile' on this also. Restart your phone and now you should be good to go. The carrier file should now update without any errors.