This is a regular occurence for me, but fear not it is fixed SIMPLY.

You can always revert back to the shipped ROM very easy.

If you have unlocked your phone with coke 2.31 or 0.40 (You check this by hitting the power , camera and reset button all at the same time)

if it does say one of those two, you can put on the memory card that came with the phone the nbh file attached to this thread

http://forum.ppcgeeks.com/showthread.php?t=24906

all you have to do is get the file on the card, make sure your card is FAT 32 (right click on the card in my computer (when its in your computer) and it will say FAT or FAT32 , if it says FAT, right click and choose format, then fat 32 and make it a quick format. Place the NBH file on the card, then put the card back into the phone, and enter that screen where it says coke 2.31 or 0.40 and it will load from there.

You can also simply connect via USB and download the new test rom from sprint on this board , run the exe on your computer and it will install windows mobile 6.1 , gps rev.a (I think) update for Sprint itself (no need for alltels).