Several members who are using custom roms have had similar problems. These have been solved by re-flashing the stock rom and radio, then flashing back to whichever custom rom they wish. Since you are with Sprint, you may want to read this thread:
http://forum.ppcgeeks.com/showthread.php?t=51298
Post #8 in this thread will direct you to the various shipped roms posted, or just go here for the Sprint shipped rom and download:
ftp://ppcgeeks.com/Diamond/Stock%20R...nt_Shipped.rar
-Ambrose