[Galaxy S I9000 General] currydude:
!IMPORTANT! - CHECK FOR POSSIBLE DATA CORRUPTION​

Quick Steps to check for possible data corruption:

1. Navigate to LOST.DIR Folder in Internal/External SD card using any file explorer (My Files, ES File Explorer, Astro Explorer, etc.)

2. If this folder is empty then you have nothing to worry about - no data corruption! Otherwise, delete ALL of these files (Labelled with various numbers)

3. Reboot device/Restart media scan for internal/external SD card

4. If files reappear straight after reboot/rescan, then there's a possibility that there are damaged files located on the phone or your SD card is damaged/error with file system used.

[If LOST.DIR folder remains empty after reboot/rescan then your SD card/DATA is safe]

Locating damaged files:

- Open the file using any file explorer (My Files, ES File Explorer, Astro Explorer, etc.) and choose to open as "Text" [Alternatively, you can connect/mount it to your PC and open the files with notepad]

- Text should indicate location of possible corrupted file, navigate yourself to this file

- Make backup of file on PC

- Reboot device/Restart media scan for internal/external SD card

- Check LOST.DIR again if any files are recreated, if files are again recreated, then move to next section.

SD card is damaged/error with file system used:

- If you are using a lagfix (especially those with EXT2 as LOOPS), then disable them and/or return to the RFS file system.

- Reboot device/Restart media scan for internal/external SD card

- Check LOST.DIR again if any files are recreated, if files are again recreated, then I would suggest you reflash your ROM and repartition/format

- If LOST.DIR files continue to reappear instantly after a reboot/rescan, then I would suggest you flash back to stock and contact your device maker for warranty claims.

Possible Causes for creation of files in LOST.DIR:

- Improperly turning off device, such as pulling out battery when device is still on

- Interrupted media scan

- Files copied for PC were corrupted initially

- Damaged SD Card

- Fake SD card

- Disconnecting your device when mounted as mass storage device to your PC (without first properly unmounting it)

Evidence/Reference: http://tinyurl.com/4bccju4

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Having lots of files in your LOST.DIR does not necessarily mean that you have any data corruption - As noted by some users, it is safe to have these files, but I believe if these files continuous reappear in LOST.DIR, right after a reboot, then you have might have a problem

Delete the files, reboot, and navigate back into LOST.DIR folder and if files are recreated then you possibly have data corruption, if LOST.DIR folder remains empty then you do not have to worry about data corruption

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EXTRA INFO (Edited by me - thanks to rschenck for clarification/original post):

The LOST.DIR is where the system stores orphaned, damaged or corrupted files it finds during the file system check as it boots up. It would be expected that most all of you will have at least a few orphaned files in there. They are perfectly safe to delete, however, if after rebooting the system, MORE files are created in LOST.DIR then these aren't orphans, they are corrupted files and could signal a problem.

Hopefully when you delete them, they will not be replaced at reboot and you will gain some peace of mind that their is no evident DATA/SDcard Corruption/failure

This is a very important housekeeping/maintenance procedure to extend the lives of our phone, especially for those using EXT2 or loops.

Best of luck,

Peter