Up until OS 4.2 the Blackberry Messenger application was an optional download. You simply went to the Blackberry website from your BB and downloaded it. However, beginning with OS 4.2, RIM decided to bundle the application in the standard OS package and preinstall it with each device. If for some reason that version gets removed the download from the Blackberry site will not work. The app will install but will not show up on the device. Here are complete instructions for successfully installing/reinstalling BBMessenger to your device if you have never used the Application Loader in Desktop Manager before. Handheld OS 4.1 and below:
If your device is running OS 4.1 and older then simply download BBMessenger version 1.0.94 OTA from www.blackberry.com/messenger Handheld OS 4.2 and above:
The above download from the Blackberry site is not compatible with handhelds running OS 4.2 and above. The Blackberry Messenger application is already installed with the OS and should already be on your device.
However, if the app gets removed for any reason and you need to reinstall BBMessenger on your 4.2 device, follow the instructions below. If you attempt to download and install the OTA version to a 4.2 handheld it will install ok but will not show an icon anywhere on the device. However, it will show up in the list of installed applications in Options >Advanced Options. Note: Before beginning, if you've already downloaded the OTA version and can't find it on your 4.2 device then first remove that version by going to Options >Advanced Options >Applications and deleting Blackberry Messenger v1.0.94.
Installation of BBMessenger for 4.2:
1. Determine your specific OS version by looking in Options >About.
2. Download and install the latest Desktop Manager 4.2 from here.
3. Go to your carrier's OS upgrade site and download and install the matching version of the OS to your PC. OS upgrade sites can be found here. Note: If you've already installed the OS or another carrier's OS to your PC then you can obviously skip this step. If a newer OS is listed then continue with these instructions and you'll get a new upgraded OS at the same time. If you're just installing the BBMessenger and not doing an upgrade it only takes a few moments. However, the full upgrade process can take up to an hour and will show a spinning hourglass on the device for up to 20 minutes at a time during the process. Don't get impatient and unplug the device until it's done during an OS upgrade.
4. Plug in the device and open Desktop Manager. Run Application Loader. You should see a list of installed applications with checkboxes next to them. Check the box for "Blackberry Messenger." Then simply hit next, finish, etc. to load the application to the Blackberry.
When you are finished you should have successfully reinstalled Blackberry Messenger back to your device. It generally shows up on the home screen or in the Applications folder. Happy BBM'ing.