Corrupt User Account?

We had a fleet of Palm Treo 680s (Palm OS) and we are replacing them with
Nokia e63s. All has gone smoothly, just installing the Intellisync
client, then swapping the SIM card and I'm done. Then the last two users
(one being the president of the company, of course) fail. Email syncs,
but calendar and tasks don't. Then, within an hour email starts
duplicating.

I tried deleting the user, then letting the e63 create the account; same
result. I did a hard reset on the e63 and installed the client with my
credentials and it works fine. I changed the credentials to match the
problem user, and the issue returned. Is there some "residual data" or
anything when you delete a user? It seems to be user account related
somehow.

TIA for any advice.