So far this has been the only sure fire method I've found to 100% get around any brick situation regardless of firmware, etc. This only works for the captivate, not any other galaxy s variant.
Situations: phone-!-Computer / no download mode
Black Screen / RST_STATUS 0x0
1. Remove the battery, external SD card and SIM card.
2. Wait 10 seconds.
3. Open odin3
4. Connect usb cable.
5. Hold volume up + volume down + Power.
6. Insert battery.
7. Release POWER BUTTON ONLY.
You should now be in immediate download mode.
Please forgive me if this is duplicate some where, but I tried every procedure I could find on google to no avail, then accidentally found this method just before I was going to box it back up and see if my buddy at AT&T would make me eat it or not.
My situation was: Launched Odin3 to flash H3 firmware, died twice in the middle, and on the third time locked up half ways just at the beginning of factoryfs.rfs -- Then the phone did nothing. Blackscreen is all. Interestingly enough, while in the state if you hold volume up + power, it will give a hw diagnostic screen. Beyond that I could get no where. Just a black screen, no acknowledgement when connected to PC, no charging indicator, nothing.
If this is a dupe Im sorry but this method I could not find and hope to make it readily available to people who may think their phones bricked.
How to BRICK the phone / WARNING!!!
If for whatever reason you decide to use Odin to flash a stock GTI9000 ROM and manually add the kernels and modems using a "pure" 2.2.1 sammy rom. BEWARE.
Researching a lot, it seems the consensus is that the sbl in the 2.2.1 versions of the GTI9000 has *hard* download mode crippled.. Meaning if there is a software screw up YOU CANNOT USE A USB JIG OR ANY OTHER METHOD OF GETTING THE PHONE IN DOWNLOAD MODE!!! To fix it you'll need a new one or JTAG to replace the bootloader.
As far as I can tell, beyond getting completely rid of the AT&T logo, there is no need to flash boot/sbl to get the "purity" of the 2.2.1 sammy roms.
Extract all files from the tar EXCEPT boot/sbl and re-tar and flash just those to avoid overwriting the stock captivate boot loader.
Also, it does not appear the boot/sbl from the captivate 2.2 leak suffers this same problem.
For any one iffy on bricking their phones, stay away from roms that remove COMPLETELY the AT&T logo on boot. This generally means the boot loader has been messed with any you may be screwed if you soft brick the phone. Most CWM roms dont overwrite the boot/sbl, but some can and do. Watch yourself.. if it the AT&T logo goes away COMPLETELY, I recommend flashing JF6 with One click while the roms alive using adb reboot download and try another rom.