Try Try and Try again
Yiour other possibility is to keep on trying. Your passkey is hashed with user information.
If installation of software changed user information, you will need to try and find a combination resulting in the same hash value(very slim possibility, almost impossible)
Other option: Hard Reset..
I know ths doe not help, but these are the possibilities AFAIK
HTC P3300 => HTC touch HD => HTC HD2