[Samsung Mesmerize] 93foxgt:
First off i would like to thank Veteranmina for his right up on this issue. I'm just copy/paste from his thread for you guys here at XDA.

First off I want to say that I am not responsible for anything that you do on your phone that can make it a expensive coaster plate. You take full responsibility for YOUR actions.

***Phone will be wiped as so you will loose all data currently on phone that is not backed up, I am not responsible for any data loss***

***If you are on ext4 DISABLE VOODOO***

THIS IS FOR THE MESMERIZE ONLY

These are stock odin loads so you will loose root access

There is a known radio issue that in the event if you receive a US Cellular Galaxy S Mesmerize with 2.3 Gingerbread EH09 you will not be able to use older radios EC10 and EE19.

If you do attempt to downgrade to an older radio/modem i.e. ec10 or ee19 your phone will not show a baseband present and possibly wipe your phone number/meid off your phone.

To fix this issue follow these steps to restore your phone back to EH09 depending on your file system.

***If you are running MTD***

1. If you do not have Odin download this http://www.megaupload.com/?d=3MEL5ZKY

2. Download the full EE19 2.2 Froyo Odin with 2.2.1 .Pit file http://www.megaupload.com/?d=3CPY7VQW

3. Download the full EH09 2.3 Gingerbread Odin With 2.2.2 .Pit file http://www.megaupload.com/?d=TDXMIEL9

4. Unzip odin files

5. Open Odin3 1.83.exe

6. Put phone into download mode (turn phone off and hold volume down button and plug phone into computer or pull battery, plug in and hold volume down button)

7. Make sure to select re-partition.

8. Use the froyo 2.2 EE19 files first. Load the .pit file in the pit box and the md5 file in the pda box.

9. Make sure to select re-partition

10. Hit start and let odin to its mojo.

11. If you took battery out to go into download mode you can reinsert it during or after odin is finished.

12. Let phone boot to format system to needed filesystem.

13. once booted turn phone off and repeat steps but with the EH09 md5 file (do not need the .pit file) and DO NOT hit repartition for this step

***IF YOU ARE RUNNING RFS/EXT/EXT4***

1. If you do not have Odin download this http://www.megaupload.com/?d=3MEL5ZKY

2. Download the full EE19 2.2 Froyo Odin with 2.2.1 .Pit file http://www.megaupload.com/?d=3CPY7VQW

3. Download the full EH09 2.3 Gingerbread Odin With 2.2.2 .Pit file http://www.megaupload.com/?d=TDXMIEL9

4. Unzip odin files

5. Open Odin3 1.83.exe

6. Put phone into download mode (turn phone off and hold volume down button and plug phone into computer or pull battery, plug in and hold volume down button)

7. For the first round use the EE19 files place the md5 file in the pda section (do not need the pit file as you are already have the correct file partition unless you cannot turn off voodoo)

8. Hit start and let odin to its mojo.

9. If you took battery out to go into download mode you can reinsert it during or after odin is finished.

10. Let phone boot to format system to needed filesystem.

11. once booted turn phone off and repeat steps but with the EH09 md5 file (do not need the .pit file)

After you've gotten this all done and have avoided making your phone a coaster, dail *228 to regain your phone number if you lost it in the process of trying to downgrade modems.

As for the Showcase and Fascinate I do not know if there is any issues with radios on the newer phones. This is for the mesmerize and mesmerize alone.