Unexpected, random shutdown and require a battery reset to power on again (5+/day)

[xenub]

My brand new HTC Diamond keeps shutting down on me! :confused:
It never shutdowns while I'm actively using it (even when I browse a site that max out my memory), so I suppose it happens only when the screen is off. Many times a day, I try to use my phone and realize it is off and it wont power back up until I open the case and reset the battery. I've tried to find similar problem report on this forum, the only post I've seen the person seems to experience similar problem but there's one symptom I don't get : on my phone the battery charge level always reports a credible/expected amount.

Its my third mobile in a row that behave like that (Motorolla -> LG -> HTC). I feel like I'm cursed!

I'm suspecting a faulty battery even though its brand new! That will be my next move, yet in the meantime I'd like to know more about what that behaviour implies : needing a battery reset?

Currently use (but it has the problem since I have it from Rogers!):
HTC Touch Diamond, Q7201A
ROM: Energy Rom july 4th 2009 WWE
Radio: 1.00.25.06
SPL-1.40.OliNex

Thanks!