For an Error 721 when connecting using a Blackberry, it is almost always a device issue and requires pulling the battery out. This often occurs when an established internet connection is interupted by unplugging the phone from the computer prior to disconnecting. This typically only affect Blackberry phones.

Basic Troubleshooting - Always do this prior to more advanced troubleshooting

1. Verify the phone can browse the internet
   Note If the phone itself cannot browse, this is likely a device/network issue and you should contact your wireless provider.
2. Pull the battery out of the phone with it disconnected from the computer and power.
3. Restart the Computer.
4. Test the connection again.

Advanced Troubleshooting - Do this is basic troubleshooting fails to resolve the issue

Backup the Blackberry data to the computer then do a Master Reset

Perform a Backup:

1. Connect the Blackberry to the Blackberry Desktop Manager
2. Select Backup and Restore on the Blackberry Desktop Manager
3. Select Backup
4. Save the Backup to an easy to find place on the PC

Wipe the Handheld:

1. On the Blackberry go to Options > Security Options > General Options
2. Press the Menu key (the key with the dots)
3. Select Wipe Handheld
4. Enter Blackberry then select Continue
5. The Blackberry may take a few minutes to reload
6. Prior to restoring the backup, attempt to connect to verify if this has resolved the issue. If the issue is resolved, restore the backup and test again. If it fails after restoring the blackberry, there is likely some corrupted data on the Blackberry.

Restore Backup:

1. Connect the Blackberry to the Blackberry Desktop Manager
2. Select Backup and Restore on the Blackberry Desktop Manager
3. Select Restore
4. Select the Backup file created previously to restore the data.