If you have your master password, try checking if you have the "correct set of keys" on PeakD.
At the upper right hand of your profile page, click Account Actions > Keys & Permissions > Reveal All Keys > Input your master password.
This will reveal both your public and private keys. Copy/back up and save it somewhere safe...
If you already have the correct set of keys with you, you may now change your password using your Owner Key.
Hope this helps...