iPhone 3GS/3.1.2 - Can someone make this clear?

[Tralce]

I currently have an unjailbroken iPhone 3GS running firmware 3.1.2 and I have had no luck jailbreaking it. Is it possible or is it not possible? Tethered or untethered? How? A link to a tutorial would be great.

On a side note, several months ago I used some utility on OS X (back when I had a mac) and it did jailbreak the phone, but it would no longer function on AT&T's network. Now, though, I can't even get that far.

I sync the phone using the latest iTunes in a TinyXP virtual machine, but do have a functional Windows machine if need be.

Please sort out this confusion!

I've tried QuickPwn and blackra1n, and neither will do anything at all.

[sursture]

1 - Use Blackra1n, download here: blackweather [select windows or mac based - click icon at the bottom of page]
2 - put the phone in Restore mode [turn off!, Hold n keep holding Home button, connect to PC, let go of Home button only when you see the "connect to iTunes" on the phone]
3 - Run blackra1n.exe
4 - Install Blacksn0w (Optional: If you need 2 unlock)
5 - Install Cydia (gives u options to install alternative apps)
6 - Unlock with Blacksn0w (Optional)
7 - Keep smiling

Dead simple - a 2 min job - now detailed instructions required

[Tralce]

1 - Use Blackra1n, download here: blackweather [select windows or mac based - click icon at the bottom of page]
2 - put the phone in Restore mode [turn off!, Hold n keep holding Home button, connect to PC, let go of Home button only when you see the "connect to iTunes" on the phone]
3 - Run blackra1n.exe
4 - Install Blacksn0w (Optional: If you need 2 unlock)
5 - Install Cydia (gives u options to install alternative apps)
6 - Unlock with Blacksn0w (Optional)
7 - Keep smiling

Dead simple - a 2 min job - now detailed instructions required

Hey, thanks for the fast reply. However, I've done this exactly four times. Blackra1n does its thing, and everything seems to work wonderfully, apart from the complete lack of the phone ever rebooting. I'll let it sit there with a black screen for three hours or more! it eventually reboots, and there will be no Cydia icon anywhere, or any indication that the break was in any way successful. Once, it rebooted after the aforementioned three hour period.

Any ideas?