I don't think there is any sync app or agent deposited on the phone. At least, I did not see one.
1) you have to set up the phone in Blue tooth as a paired phone FIRST, before you set it up in iSync. Delete the phone from iSync, BT, etc. and restart. Also, delete the computer from BT on the phone. (You can only pair with one computer for syncing, although you can send files, photos etc, with more than one computer or device.
2) Now you start over and pair with one computer for syncing. (Answer: for syncing w/more than one 'puter, use the iPod for that.) Be sure and check the boxes authorizing the device to sync when you set it up in BT.
3) Now go to iSync and add the device. It should show up when you scan for devices. Be sure the phone is set up to show itself.
4) On the phone, go to BT preferences. Add the computer as an authorized device.
5) Set up sync for the first time.
6) Close iSync. Start sync from the control bar at the top of the screen.
If you still have an error, go to iSync and find the Synclog command under Window. Look at the log, It may give you some ideas if you are still having problems.
Also, Symbian phones seem to work when you turn the phone on and off a couple of times before syncing.
MW