I have a BB 7520 and use the Blackberry web service to push my email. Often, I will receive the same message two and three times from the same person. It only pushes to the BB once not multiple times like the desktop. Does anyone have any idea what is causing the problem?

Do you have it set to keep your messages on your other services, or do you move them all into your BlackBerry web client? I've seen issues when people didn't delete messages from their other accounts when it transfers into the BlackBerry Web Client.