I have a 3G on Tmobile.
I originally had a problem w/my gps, and learned that since I updated to ios 4.2, baseband 6.15, it screws up the gps. So I found a way to downgrade the baseband, as was just recently figured out earlier this year.

I used Redsnow to downgrade the baseband, and followed some instructions here: How To: Downgrade iPhone 3G/3GS from 6.15.00 to 5.13.04 AND fix Cydia apps + unlock. And since I was not able to go online on my phone, the link had a way to copy the deb files via my pc (ifunbox) for the mobilesubstrate and ultrasnow.

Thing is, when I restarted the phone, as per the instructions on that link, and looked in the directory (via my pc) both files had vanished. i don't know if something went wrong or if they were moved.

Anyway, I don't think the whole procedure worked b/c now I cannot get wifi, bluetooth, no firmware is listed in the settings, and it says it cannot make calls. It also keeps restarting every few min. It's saying to factory restore it but that'll get rid of my jailbreak.

Is there anything I can do?
If I do restore it, then what os, baseband etc should I use so my gps will work again? Can you provide me w/a link or instructions?