Help Weird boot loop(?) - Options? Any hope for my data?

[OhThatEthanGuy]

So... My (boot-unlocked) (Verizon) GNex won't get past the Nexus boot-up animation. If I leave it, it'll just keep doing that until the battery dies. I unlocked the bootloader as soon as I got it (so I wouldn't have to wipe it later) but I don't remember if I ever got around to rooting it... probably not, as I didn't put any apps on this one that wanted root for anything, & I'm not one to flash custom ROMs( I was going to start experimenting with that on this GNex in a few weeks once Nexus 5 becomes my primary device*). It was running stock, the last OTA update, 4.2.1 or 4.2.2, I forget which that was( heaven forbid we should see 4.3 on Verizon).
I don't know what could have happened to cause it, except that last time I was able to use it I got an ANR for "Process system" while it was powering down as the battery died, but my friend distracted me & the charge hit zero before I managed to respond. I've had those ANRs before & used all 3 options without any ill effects, but I can imagine it might be particularly troublesome that the OS would happen to hang during its shutdown routine, followed by losing power.

I can get the bootloader up, at least. Have I got any options besides trying to format it? And if not, is there any hope of retrieving data? I didn't have a ton on it that wasn't also in the cloud, fortunately, but it’s been a while since I backed up my SMS messages, and there were photos I would surely miss.

EDIT: Of course I should say what I already tried, as Hadron's reply reminds me. So, I already pulled the battery & left it out for quite some time, to no avail; clearly something serious is screwed up. I started up the bootloader successfully, though, & I connected it to my PC via the USB cable; the PC recognizes it so I should at least be able to attempt whatever suggestions anyone has for backing up data.
I would normally have explored in greater depth what I can do via the connection before bugging other people for help, but my only currently-working PC hates the Android SDK & the ADB for some reason; I'll have to borrow a computer from a friend, so I was hoping to gather suggestions beforehand in order to make the most efficient use of my limited time on whatever machine I end up using to interface with my poor, troubled GNex.

(*I'm fully aware that Nexus 5 isn't likely to work on VZW; fine with me, I'm sick of waiting for updates from big red.)

 

[Hadron]

Ok, I've never owned a GNex, so hopefully you'll get better/more detailed answers from those who know it better. These are just the generic ideas which occur to me.

First and simplest, pull the battery out for a couple of minutes. If you've got some stuck bits in the RAM this will clear them. Then see if it boots.

If not then we're probably looking at a factory reset. But you may still be able to save some data. Since the bootloader is unlocked you could try installing a custom recovery (even temporarily if that is possible on a GNex) and making a backup with it (a "nandroid" backup). That way you still have a copy of your data. Of course if you simply restore that backup you'll restore the problem, but you may be able to recover some of the data from it (e.g. if you were to root then Titanium Backup Pro can restore user apps/data from at least some types of nandroid backup).

Maybe others will have other ideas, but it's all I can think of. Other types of backup require the phone to be running. Though actually if you have an adb daemon running maybe you could try an adb backup too - a custom recovery should include that, so if you were to install one of these maybe you could try that too (also needs a usb lead and adb installed on a computer).

I'd hope that at least you could do a factory reset which would leave your photos intact, rather than wiping all storage.

Good luck