Recovering lost admin password

It appears that our administrator password has changed/corrupted. Is there a way to reset the password?

Unless you had set up an ID escrow agent (R4) or password recovery (R5), you may be out of luck. There is no feature to "reset" a password in a Domino/Notes ID file. However... all is not lost. Do you still have the Certifier ID and its password? If so, you can make a new administrator ID with the same username. That is the easiest route.