This has happened to me a couple of times. First when JBing my phone, then when JBing a friend's phone.
With my phone it hung at the Apple logo when I jailbroke with all my apps and stuff on it so I just did a full restore, then jailbroke in the fresh state, and there was no issue, then synced all my stuff back on.
But somewhere else I saw a forum post by a guy who said it happened to him and he just waited a while and then force-shut off the phone and eventually it came up fine.
So with my friend's phone, it stuck at the apple logo, we let it sit there for like half an hour, forced it to shut off by holding home + power buttons, then turned it back on. We were still stuck at the apple logo.
So I said F-it, not working, we're going to wipe it as a new phone and JB in that state, then sync everything back onto it. I got ready to put it into DFU.
The phone was plugged into the computer (so iTunes would see it as soon as it hit DFU mode). I held down the home button for 10 seconds, and as I prepared to hit the power button as well (beginning the DFU sequence), bam, springboard popped up, his phone has been working fine ever since.
Don't know if that helps, but hope it does