Ok, so check out these two screenshots that I took within the past 3 days. The first one, at 9:53am...after charging it all night, my battery life was at 52%! Then at 10:06am it drops by 50% to 2%.....WHAT?????!!!!!!!!
Second screenshot happened last night! I checked battery life and it was at 80%...turned on media player, from 8:25pm to 8:46pm it dropped by 72%!!!!!!!
Its gotta be a faulty battery right???
If the phone is not "warm or hot" to the touch on the back and you see no constant data transmissions during this time, then it has to be a bad battery. If the phone is getting warm, then you have something running in the background that's either pegging the CPU and/or using the radio a lot. I'd start by asking myself if you've made any recent changes (added programs, changed settings, etc.) and if not, and the above doesn't hold true, then it's most likely just a battery going bad.
I noticed you're running the .451 hybrid, right? That might actually be the problem. I've noticed that battery life with the hybrid is completely wonky. Sometimes it's great, sometimes it plummets like a brick. And that's with battery pulls and OS reloads (although it did settle down after the last OS reload). You can try reloading, or try a different hybrid, or you can try downgrading to straight .419.
I notice that when I charge my phone, if I don't charge it completely, the battery charge indicator reads significantly higher when I first take it off the charger. I have never scene a 50% drop, but 10% in the first 15 mins is not uncommon.