I just got an 8100 for a user. Prviously he had 2 devices, an phone and an old blackberry. I added a data plan to his phone number and did a wireless activation from his new 8100. A few hours later began getting duplicate emails. Sometimes 3 or 4 copies. I wiped the handheld, uninstalled the desktop manager software and did another wireless activation and were still getting duplicates. Has anyone ever seen this before?

You'll need to be more specific. Are you on a BES or BIS? Is the duplicate emails from the BB email address?

I have seen duplicate emails when people have been on BIS and then go to BES but forget to remove the email address they from the BIS.
So the BIS will be pulling a copy from the email server and forwarding it to the device and at the same time the BES will be forwarding emails too.
Does that make sense?

BIS, BES, or both?
Open up the duplicates and scroll to the top. What is listed in the received using field for each?