BES 4.1 / Exchange / Server 2003 Std

We have one user then when she travels she suddenly cannot send. She is in major market areas with coverage but starts to get those ominous "This message is used to carry data between the BlackBerry Handheld " messages and cannot send. She can recieve emails just great and the BES server says its talking to the device. All other users can send without problems and when she comes back from the trip I usually reset the device and she is ok.

I really don't want to make her clear her device and that dosent always fix the problem. What could be happening to make it stop being able to send?

Any help would be appreciated.

Does the user have the correct date and time on the Blackberry? I know that if your blackberry does not have the correct time the user will not get email. I've found that message in the past to happen when a user either isn't activated on the BES or when the user is first being set up on the BES, that is usually the text of the network message you get.