Sorry for the cross-post, but since XDA insisted on making separate forums for Inspire 4G versus Desire HD, you should probably know that there is already a RUU posted for Inspire 4G.
I got it from this thread:
Here new RUU for ACE Cingular US
Please verify that the build and radio numbers match your device before you embark on any modding attempts. If so, then this RUU is your de-brick-it ticket to stock.
If you have flashed a higher version RUU and you don't already have S-OFF, and it thereby won't let you downgrade to this stock ROM, check out the downgrade thread:
but use this RUU instead.
STOCK ROM in ZIP FORMAT
Place this .zip file on the root of your SD card. Disable fast boot in settings > applications. Turn off your phone. Hold down the volume down button and the power button at the same time. The phone will reboot into hboot. It will load the ROM automatically. Follow the steps to flash the ROM.