I had the same problem with mrom6. You need to do the following:
1) Download the stock rom. See HTC site or sticky note for
http://forum.ppcgeeks.com/forumdisplay.php?f=67 (I downloaded the alltel rom from the htc website)
2) Boot the phone into the bootloader screen (multicolor screen). See previous posts or
http://forum.ppcgeeks.com/forumdisplay.php?f=67
Boot to multicolor screen:
i)Pull battery, wait 5 seconds
ii)Put battery back in
iii)Press the Volume Down button
iv)While holding volume down, press and hold the power button, this will put you into bootloader(tri-color screen)
v)Plug in USB cable
vi)Flash
3) Install stock rom while multicolor screen is displayed.
4) Hard reset the phone
There are two main methods:
i. Power + VolumeDown + Enter (circle button) and hold down Reset until the white screen appears, then press VolumeUp to Hard Reset.
ii. Goto Start > Settings > System > Clear Storage. You can then choose to Clear Storage, Format internal storage only (the 4GB memory), or Clear storage and format internal storage. Once you've made your choice, type in 1234 to the box at the bottom, and then click Yes.
5) Installed mrom6 via normal methods.
This worked for me. Thanks.