That happens if the phone’s internal memory (or SD card) contains files with extensions longer than 16 characters.
Everything is explained here : http://androidforums.com/samsung-galaxy-s/157617-solution-tutorial-galaxy-s-i9000-mtp-application-crashing.html
Especially look for the post by PhoenixFx. He wrote a small .NET program that will scan the phone mass storage for the problematic files.
- Download PhoenixFX program (find it here)
- Connect the phone as Mass Storage (make sure you “mount” the drive of the phone)*
- Perform the search using PhoenixFX proggie
- Delete the files found
- Reconnect the phone in Samsung Kies Mode*
*options to change behavior when connecting the Phone to the PC with USB are to be found under “Settings / About Phone / USB settings”