Well, now I've done it, I can't get my phone to power up

When I hold down the power button to turn it on (was doing a full reboot after updating some sofware on Rock, more details below) I get the pwnage tool pineapple for about 5 seconds and then the screen blanks out and the device is dead. Multiple attempts give the same result.

I have a jailbroken 3GS with an untethered pwnage jailbreak for 3.1.2. Just before this happened I had finished running a bunch of updates on Rock, but it was nearly all underlying application kind of stuff. Backgrounder was the only one I really recognized as an app I actively use. I had also just completed a recommended update to Rock itself. Once the updates were complete and the phone finished successfully soft-rebotting, I powered it down to do a full reboot in order to free up any leftover memory that was being held up. Now it won't power up. Awesome.

I'm at work right now and don't have a computer I can connect it to, but I'm not sure what good connecting at all will do at the moment so hopefully someone has been in the same situation and can give some advice.