I'm sure it's just my rather confusing sytax: your command of English is very good - I didn't realise you were a non native speaker.
Perhaps the confusion is arising from my understanding of the situation - correct me if I'm wrong here:
- Your activesync is working normally (with the occasional connection glitch, but we all get these). You have the desktop conflict settings set to "Always replace the item on this computer", because you use the XDA as the main entry point for new items.
- You can do a full backup no problem
- When you come to restore the backup, after a hard reset of the device or total power-down, there are problems replacing items on the device becuase the files are considered in use.
- After the backup, on the first synch, all contacts and appointments are duplicated.
So my suggestion was to:
- Synch as normal, so that everything is correct on your PC
- change the conflic resolution to "Always replace the item on my device"
- Un-cradle, remove startup links, soft-reset, re-cradle.
- Do the restore
- Un-cradle, soft-reset, re-cradle
- Synch again, so that everything is correct on the XDA
- change the conflict resolution back to "Always replace the item on this computer" so that new items are taken from the XDA.
If all else fails, I've heard good things about Sprite backup: