ActiveSync, Smartphone, and Small Business Server

Summary: o2 XDA smartphone used to work fine synching to SBS 2003 server.
Now it won’t synch past a certain day.

Background: My client was having a problem getting his smartphone to
synchronize contacts as he uses shared contacts. At the time I didn’t
realize that you couldn’t synchronize shared contacts (now I know that you
can’t synch shared contacts – hopefully this feature will come soon as all my
clients use it). Anyway, I ended up mucking around with his sync settings
and converting contacts and inbox to sync from his local machine. I did this
by disabling the sync on the PDA and then enabling it on the local machine.
I didn’t set up a new partnership.
Anyway, since then I have tried to convert it back to server partnership
tha gets contacts and inbox and calendar from the server, but when the phone
synchs, it works fine no errors, but never downloads anything in the inbox
past the date that I mucked it up. I also don’t get contacts (didn’t check
calendar). All this with no errors.
I have tried creating a new partnership, doing a soft reset of the smart
phone, and downloading everything again, but this hasn’t helped.
Going to the Exchange/oma website works fine and I am able to log in
successfully to the authentication using my clients username and password.
After some more reasearch and reading the MS webcast on activesync and
exchange, I figured that the state files on the server were stuffed so I
tried deleting the webserver/exchange state files as detailed in the
Microsoft webcast, then doing the new server partnership and redownloading,
but this didn’t help.

I don’t claim to be a PDA / activesync guru, but am ramping up quickly. I
would prefer not to do a hard reset on the device without just cause. Is
there a way to clear all remnants of the previous connection from the server?
Maybe I did it wrong before? Maybe I’m chasing a red herring?

At this point, I currently have the client synching to his local machine as
that is the only way I could get his contacts back. Obviously this is sub
par when he has been using the synch over GPRS in the past.

Can anyone offer some suggestions on where to go from here?