3G won't TURN ON, won't RESTORE!!! HELP!!!!

[messedupiphone]

I just got a 3G and I installed Cydia using redsn0w 0.9.6b. I then realized that many cydia apps don't work on iOS 4.2.1 so I figured I'd downgrade it to 3.1.3.
I downloaded the 3.1.3 firmware off some site and shift-clicked on 'restore' in iTunes, selected 3.1.3 and it got started, everything seemed fine, the iPhone showed the Apple-Logo and a progress bar that was slowly filling up.

Toward the end I got an error message though and it didn't complete. Ever since I can't turn on the phone regardless of whether it's plugged in or not, holding down the Power and Home buttons simultaneously won't do anything either.

When I start iTunes it tells me the iPhone's in recovery mode and needs to be restored. I then click on restore -> window pops up i click on 'update and restore' and the same thing happens -> at the end it aborts and gives me "The iPhone 'iPhone' could not be restored. An unknown error occured (6)."
I just tried again and the error was (37).

I have absolutely NO CLUE what I can do to get it to work again, since I just got it there's no data on it and any tool or method is appreciated no matter what it does (delete/wipe iPhone, no problem as long as the thing will work again)
Of course I would prefer to 'restore' it to 3.1.3 if possible, but for now I just care about the thing becoming operable again!

Do any of you know any tools/methods that could do the trick here? I'm desperate any input is appreciated!!!

[vaillage]

Seems that you are in a DFU loop. You downloaded it from SOME site? Are you sure you didn't download a damaged/unofficial custom firmware file? That's where the error 37 points out.

Error 6 is trying to tell that you may need to try a different USB port. (Restart computer after doing this)

Download a clean firmware file (and last known operable one) from iClarified and shift-restore your iPhone without pointing your hosts file to Cydia.

If a clean restore does not do the trick, try using redsn0w to force the device in a pwned DFU, and try restoring to a custom 4.2.1.

[messedupiphone]

You downloaded it from SOME site? Are you sure you didn't download a damaged/unofficial custom firmware file? That's where the error 37 points out.

I'm sure the problem is not with the firmware - I downloaded 4.2.1 and 3.1.3 from iPod, iPhone and iPad Firmware Download - i now also downloaded 4.2.1 from iclarified and it matches the size of the one I already had -> unfortunately it also matches the result

Error 6 is trying to tell that you may need to try a different USB port. (Restart computer after doing this)

I've tried different USB ports but strangely enough I now only get error 37 independent of the used USB port.

I've already tried it with iREB too - i got the green screen but again it didn't change anything it still completes almost entirely and in about the last 3 percent when it comes to the verification process it aborts and spits out error code 37.

As a result I presume the problem is with this ECID SHSH thing cause I guess that's what they check in the end - when I got the 3G (just the other day) it was already on 4.2.1 and I didn't extract/save ECID SHSH or anything - at least not consciously - I just used redsn0w to install cydia and then tried to downgrade to 3.1.3 (via shift clicking on restore and browsing to the 3.1.3 FW) because a lot of apps didn't work on iOS 4

however i've read something along the lines of cydia automatically uploading the shsh to their servers in the newest version - is that true and if so how do I take advantage of this?

Isn't there any other program besides iTunes that is capable of changing/updating/downgrading an iPhone's operating system or any method that allows for this to be done offline without this annoying very faulty verification process??

SOLVED

Unbelievable as it is all I had to do was to shut off Zone Alarm Firewall during the restoration process and it worked like a charm