Well unfortunately you might have radio hardware failure, or even motherboard.
Not knowing what all you flashed, like accidently downgrading radio from gps to nongps, which can brick if you don't know what you are doing. It is hard to tell.
One thing to check, when first splash finishes, the radio turns on, which can be seen by the led's coming on. If they never come on and you know you had a good radio flash, then you may have a bricked device.
The best I can tell you at this point is, run the stock sprint ruu which contains rom and radio combination. If it boots, where it says tap screen to align, don't tap, soft reset device, that will keep the sprint customizations from running.
Here is a link to that rom:
HTC Mobile Phone Support - HTC Mogul™ (Sprint) - Downloads
Version 3.56.651.0 | 02.01.2010
Good Luck.