Uninstall any copies of the Blackberry Desktop Manager that you may have running
The Blackberry Desktop Manager software is the second-most-common cause for Enterprise Activation failure.
If you have a Blackberry device but don’t use Blackberry Enterprise Server, the only way to synchronize your non-email Outlook information with it is by connecting it to your PC via USB or Bluetooth (or if your Blackberry is really old, by using a serial cable).
Blackberry Enterprise Server replaces this desktop-based application, so it no longer remains necessary. Furthermore, if you have previously associated a Blackberry device with your mailbox using the Desktop Manager and it is running while you attempt a wireless activation, the activation will fail because the Desktop Manager will essentially hijack the messages that are intended for the device.
To uninstall the software on Windows XP, choose “Start – Settings – Control Panel – Add or Remove Programs”, select the Blackberry Desktop software, and click “Remove”.
To uninstall the software on Windows Vista, select “Start – Control Panel – Programs and Features”, select the Blackberry Desktop software, and click “Remove”.