I've just upgraded my phone from a 6210 to a 6310i.
I have a Windows XP PC with a USB IRDA adaptor (SigmaTel USB-IrDA dongle) and PC-Suite v4.81 installed.
With the 6210, I was successfully able to sync with Outlook to the phone.
However, when I place my 6310i in front of the IRDA adaptor, Windows initially recognises it correctly and it appears in Nokia connection manager. A few secs later, Windows says 'wireless link interrupted' and the phone disappears from connection manager. This cycle then repeats.
When I start PC Sync from the PC-Suite it says 'Your phone is not connected. Please connect your phone and try again'. This happens even when the phone is appearing in Connection Manager!
This all worked fine with my 6210 and I'm beginning to regret upgrading.