We have a windows environment (W2K3R2)
Nokia phones (E90-E61)

We notice that after a period, without any reason why, some users het all their items double, or even multiplied. (mail-calendar-sent items- etc.)
After removign the user, reset the device, it works again, but after a while it starts again. It is a lot of work and try to explain it to the user

Can anybody tell me what is wrong, what to do. or how to solve it ones and for all....