Was this phone previously rooted in order to use it on a different carrier? Did you ever do anything to modify the MSL of the phone?
There are a bunch of different ROM files on the page you linked to. Which one did you download? Did you download directly to your phone, or to a computer first? If the downloaded file is on a computer, what is the filename? If it's only on your phone, can you access the phone storage at all? Maybe by connecting to a computer? I'd like to know exactly what ROM file you flashed.
I'd try following the procedure in this thread:
http://forums.androidcentral.com/sp...-30-2012-sprint-only-unroot-return-stock.html
If that doesn't work, take a look at this thread and see if anything helps:
http://forums.androidcentral.com/sp...elp-insert-sim-card-error-sprint-network.html