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Ashland. Nice town!
The iSync Palm Conduit does a relatively poor job of synchronizing Palm OS data structures. For many, there is no mapping at all, and for some—like addresses—a field label selection will determine if the data in the field is synchronized. These issues are manifested to a greater extent in 'advanced' Palm OS 5.4 or greater models, like your Treo 650.
IM messaging identifiers, like those used with iChat, are an example of a field which is not mapped. Other fields in records, such as first and last name will synchronize, but the IM data will not.
Most such limitations are addressed by the Missing Sync for Palm OS, which you can learn more about here:
http://www.markspace.com/missingsync_palmos.php
The SIM transfer problem is actually an issue with the SIM standard, which does not allow for data access other than by the mobile device itself. In order to copy contact information stored on your SIM to the Address Book, you first have to copy it to a reserved memory area on your mobile handset or smartphone reserved for that purpose. On a Palm device, that means that the information must be in Palm contact records. My SIM is absolutely devoid of any contact data, as I think that is the easiest way to avoid such issues and make sure that such information is being actively synchronized so that changes made elsewhere are actually reflected on my Treo.
Merging duplicated contacts is just one of those tasks for which there are no real shortcuts. You can remove contacts from your SIM, use UnDupe to remove any duplicate Palm contact information, and sort your Address Book records so that you can easily copy and paste information from one card to another then cut the duplicate record. There is also a merge option under the Card menu in the Address Book labeled Look for Duplicate Entries… but, I am not sure that I trust it. In my finely tuned Address Book data file, that option finds 5 duplicate records and 83 duplicated entries. I see none.
I only see dead people. (Just kidding…)
You can always back up your Address Book records using the Back up Address Book… option under the file menu, then use the Look for Duplicate Entries option and merge your records. If you don't like the results you get, you can immediately restore your record set by selecting Revert to Address Book Backup… option from the File menu.