Easiest way to clean out your contacts is to go into your Desktop Manager.
- Open up Backup/Restore > Advanced.
- From Advanced you'll see a split pane screen. The left pain is what is going to be backed up from your device and the right is a list of the currently existing databases.
- Highlight on the right side your Address Book database and click the arrow in the middle pointing to the left. This will copy the information over and prepare it for back-up.
- Once the back-up has completed, hit the Clear button at the bottom to erase and clean out the entire address book database.
- After it's finished, it will ask you if you want to save the back-up you've created, say yes and check the device to make sure the address book has properly cleared out. Now, resynch the necessary contact information and you should be set to go.