AllSync & AllDup

Using 1:1 or Update modes I'm trying to back up all data from one PC to a NAS storage. For example: C:\Documents and Settings\Anechka\My Documents\My ScanSnap\CARS\TOYOTA; \\LS-WTGL0DC\share\My ScanSnap\CARS\TOYOTA; 2008_07_08_20_43_56.pdf; 242556

It works, but seems to copy ALL files every time. At least I deduce this from the report:

26/11/2008 01:45:42 - SOURCE: C:\Documents and Settings\Anechka\My Documents\My ScanSnap\
26/11/2008 01:45:43 - DESTINATION: \\LS-WTGL0DC\share\My ScanSnap\
26/11/2008 01:45:43 - Calculating data for progress indicator...
26/11/2008 01:45:43 - Editing source -->> destination
26/11/2008 01:47:40 - --------------------------------------------------
26/11/2008 01:47:40 - PROFILE STATISTICS:
26/11/2008 01:47:40 - Elapsed time: 0:01:58
26/11/2008 01:47:40 - Files: 268 overwritten, 268 backed up
26/11/2008 01:47:40 - Data volume copied into the destination folders: 69,265.72 KB

Why does it keep overwriting the files?
What can be done to prevent overwriting ALL files?

Open the profile properties and move to Copy Modes -> Copy Rules -> Rules for Overwriting Files. Activate the option "Treat files with a modified time differential of up to ..." and enter 2 seconds. Run a copy preview of your profile and check if AllSync tries to copy all files again.