Once upon a time when I was having those kind of troubles i said f it and just loaded up a whole new fresh rom with all the spy/badware the orginal Rom had in it. No reset no un-installing anything. Did that and wow my cellular internet worked. turns out there were some different .cab files that i needed but never bothered to install. still don't know which ones. I just did that and did the manual way of getting rid of the few Sprint Addons i didn't want.
For instance when your trying to connect does your connection say Sprint Vision or something else? For me that works best. I think thats part of the orginal install settings.
