iPhone iPhone 3GS stuck on White Screen

I'm extremely frustrated and desperate, please help.
Yesterday I was given a 16 GB iPhone 3GS on ATT. I jailbroke it and unlocked it using Ultrasnow and proceeded to download apps and just enjoy it. I've had a TMobile SIM card inside of it, but for whatever reason it was never recognized, just kept saying Searching where it says Carrier.

Anyway, I downloaded Winterboard (or whatever that app for themes is called?) and it prompted me to restart my iPhone. So I did, and from there it got stuck on a white screen. I've tried rebooting it through redsn0w, and it always goes back to a white screen. iTunes recognizes it as in recovery mode, and asks to restore it, however it doesn't let me! I've tried everything, but no matter what it'll say "iPhone software update cannot be contacted" or something like that. Please help, this has been an incredibly frustrated experience.

dhlizard said:

Ultrasn0w only unlocks certain basebands

If it's an AT&T phone, I would just get an IMEI unlock from selling carrier or grey market vendor for about $5

Click to expand...

I believe I unlocked it anyway.. I think. It went from saying Carrier: ATT to Carrier: Carrier 13.0.

Either way, that doesn't help me :/

dhlizard said:

That is just the current AT&T carrier settings file
It is no indication of an unlock

If you expect to ever get a T-Mobile sim to work inside your phone, you must unlock it.

Click to expand...

Okay, I understand. Regardless, that doesn't help my white screen problems. Please?

Every time I attempt a restore, it says "Waiting for iPhone" and just stays that way.

How? I haven't dropped it or anything.