All of this sounds painfully familiar. I've been through the same thing.
Originally Posted by NuAngel
Please, PLEASE tell me there is some kind of way I can at least flash back to the factory default 8.0 ROM???
Yep! You can flash back to the 8.0 GDR2 rom no problem.
This is not a fix, just a work around.
WARNING: Be careful, not my fault if you brick stuff, blah blah...
So, after fighting the problem and trying to find the data programming and debug settings that only an anonymous Sprint tech knows (held in some secure, secret location, I'm sure), I finally broke down and flashed back to stock GDR2 using instructions and tools from various users. One note: do not use a hub or front access ports to connect your phone, even if they are powered. The drivers may not detect the phone properly. Go old school and use the back/direct USB ports.
Problem was, that left me back with no voice roaming and a camera that crashed the phone fairly frequently.
So, I dev unlocked the phone to put a registry editor on the phone. I used Blue_Frog's registry tweaks to enable Voice Roaming. For jollies (and because I wanted a fix for the camera bug), I enrolled in the Dev preview. Only difference: I never did a factory reset. Now, after the patch preparing for the 8.1 RC, my data settings were erased. Interesting, no? But this time, when I added the MMS UserProfile Info and MMS URL manually using Data Programming, it saved the info!
I am now running the latest Dev Preview (8.10.14157.200 - actually a release candidate) and have a fully functional phone. Sadly, it took 9 months, and I know others have waited longer.
While far from ideal, I wanted to post this to help others AND to help my MNVO/MS/Samsung/Sprint pinpoint the issue. Again, my MNVO and MS have been supportive, at least - which is more than I can say for Samsung and Sprint. (Though there was one Sprint tech in a store I visited who at least understood what I was telling him - maybe he's on his way to a secret bunker as we speak!)
Sorry for the long post, but I wanted you to have all the info I have. If you need further explanation, let me know.