How do I determine if my BlackBerry is "unlocked"?

From BlackBerryFAQ

To determine if your BlackBerry is "unlocked" for use on carriers other than for which it is branded:
1. On your BlackBerry, go to Options > Advanced Options > Sim Card.
2. At that screen type MEPD (see note below) on your keyboard. A new menu will pop up.

• If your BlackBerry has a SureType keyboard (71xx and 81xx devices) you will need to double-tap the P, so the actual keys entered become M E P P D.

3. Look for Network in the list.
4. If your device is "unlocked", it should say Disabled or Inactive. If it says Active, it's still locked to that carrier.

Images of Locked Device

Images of Unlocked Device

This attachment type cannot be viewed on your device

This attachment type cannot be viewed on your device

---

If you are receiving this error message when you try to open an attachment to an email this might help. My problem was that I did not have the "Blackberry Attachment Service" loaded into my phone applications. Connected my phone to Desktop Manager and sure enough the Blackberry Attachment Service Box was unchecked. I checked the box and completed the add application through Desktop Manager and I was set. NOTE: The messages that I had received prior to adding the Attachment Service still gave the error message when I tried to open them. But all messages received after installing the Attachment Service opened without any problems. If this does not fix your problem search Blackberry.com forums they listed some other fixes for this problem. The one stated above solved my problem.