Cannot Jailbreak or downgrade to 06.15.00 on my iPhone 3G, help!

[Louis54000]

I just restored my iPhone 3G with 06.15.00 BB. I wanted to downgrade BB with redsnow, but the screen remains black after redsnow writes "Done!" No pwnapple nothing. So I decided to restaure it to 4.1 (cannot go to 4.2.1 because of BB06.15.00). 1015 error fixed with Tinyumbrella. Now I'd like to Jailbreak my iPhone again and downgrade my baseband with the new version of redsnow. So I select the firmware, put the device in DFU after shutting it down, check install Cydia, downgrade BB, enable multitasking and battery percentage. It "uploads ramdisk" and then nothing, my screen remains black, my iPhone 3G is recognized as a recovery mode device, even if the screen is black, no recovery logo. PLEASE HELP! I really need jailbreak and downgrade (that's the most important)...
Thanks for you help!!!

 

[XamDam]

Read the instructions about how to do it.

Also make sure it is not a device that was manufactured in a certain time frame as if i recall the instructions
stated that certain serial numbers can not downgrade.

 

[Louis54000]

No, it's an iPhone 3G, I don't worry about the serial number. I finally got the things displayed on my iPhone (flashing baseband...), but downgrade didn't work (no service, no sim, 06.15.00 still) so I reinjected 06.15.00, I'll wait for musclenerd to release a new version of redsnow.