i had the same problem. you can not do a hard reset, because in order to do a hr you have to cut the phone off first which is impossible since the phone is stuck in the load up screen (taking the battery out won't work either). do a soft reset, press the power button, and volume up button at the same time. bootloader screen should load up. plug your phone into your computer flash whatever rom you had on your phone. if you had the stock sprint rom, here's it is. it's signed so you won't have to worry about unlocking your phone.
http://rapidshare.com/files/18080962...umped.rar.html