I've had my iDevice jailbroken for a while now. Yesterday I installed "Resupported4" and after the iPhone resprung, it was stuck on the spinning circle in the middle of the screen. Because of that, I restarted my phone and it wouldn't go past the Apple logo.

I opened RedSn0w and tried booting it into tethered. Usually this fixes it, but now it's just stuck on the pineapple logo.

Any suggestions? Do i just have to remove the jailbreak data?

Sounds like a bootloop.

Can you see the phone in an AFC2 browser at all while it is stuck on the apple logo?

Same problem here

Use the power and home to do a hard reboot and then maybe reinstall 421 with itunes,next time you might try SnowBreeze to jailbreak it,if that doesn't work maybe open itunes and hold the home button and plug in cable and keep holding home till itunes kicks the cable logo in restore to 4.2.1.