If you could post a bit more info, we might be able to help.
Are you talking about Outlook .pst files? If you are using outlook, there are a number of reasons that the information is not getting to the device.
Are you on a Blackberry Internet Service (BIS) or a Blackberry Exchange Server (BES)? What device(s) are you using.
The more info you can post, the easier it will be for us to help with a diagnostic.
"out of chaos comes opportunity"