Mepaphoros and AdamAmir:
I was facing the same situation - turn on the phone, Apple logo for a while, then the refresh spinner starts, right under the logo. Phone hangs like that forever.
I was able to fix my issue. Here's a link to my post, with my solution:
http://www.modmyi.com/forums/jailbre...urred-5-a.html
Unfortunately, you may end up having to restore the phone, but at least you'll have the phone working, right? You might try my steps on your normal computer (as opposed to using someone else's). The SIM card thing might help.
Best of luck,
Kyle