Since Alltel's MMS on the Curve is wonky to begin with, my guess is that it's doubtful that it will work consistently (if at all) on a non-Alltel released firmware.
Reportedly, getting the MMS to work was the last thing holding up Alltel's release of 4.5.
They'll let you know on their website. You just need to keep checking.
For future reference, when you want to send service books from your device, click on your manage internet email icon (the envelope with a gear in front of it)- click on service books, click on send service books.
Posted from my CrackBerry at wapforums.crackberry.com
Off the subject I have been with Alltel since 1989. I had the old bag phone. I am pleased with their service for the most part all carriers have their issues but some of the people they hire are idiots.