Wont recover, re-jailbreak, or boot tethered.

Recently i accidentally updated to 4.2.1 and had to use a tethered jailbreak. Last night the battery ran out and when i went to plug it in to my computer it would not turn on and only went into recovery mode. It always gets stuck at 30 percent when i try to boot tethered or re-jailbreak. When i try to use itunes all it does is pop up with errors half way through.