First thanks to Firebourne for posting this fix.
i had this problem too. and followed what the op suggested and the apn type would just revert to "default,dun" and not be editable when done. after an hour of messing with it i was finally able to ...
AWESOME... although the boot screen has got to go....
If you go to the taboonay web site and the kitchen section you can download a number of boot screens that are easily installed with CWM