I had the hard-resetting issue happen to me twice since installing Mighty's 4.8 last week. So finally yesterday I flashed back to Telus stock, then went ahead and flashed MightyROM 4.8 again and all seems just fine now over the last 24hrs *knock on wood*. It's bizarre how only since this ROM has this issue seems to have arised (for me, anyway).
But as a side observation that may or may not be related, both times when the device was hard-resetting itself after a
soft-reset, I had changed the default storage locations of the "My" folders from eg. "/My Documents/My Pictures" to "/Storage Card/My Documents/My Pictures" using Advanced Config in the 'Locations' section. But to clarify, the hard-reset was always sometime after (not immediately) making those changes, as in a few hours after... seemingly randomly. But just before it happens, the program icons (main ones like Contacts, Calender, etc) became some sort of default winlogo icons.
Very weird indeed.
I've learned my lesson and am no longer trying to change defaults like that... just in case.