Via the medium of MSN, I quizzed Martijn a bit and discovered the following:

Being an expert in counter-magic, Anjushree examined the broken in door and discovered several things. Firstly, it would have required being stronger that a Gryphon to open, and that it had been forced at specific points, Anjushree then tested it for magic and referenced it against my book of detailed magical notes and deduced the following.

Probable cause: An artifact imbued with vibrational magic (not a wizard using vibrational magic) had used this artifact on the hinges and handle to loosen the door. The artifact had apparently been enchanted for a long time, but it was a fairly common spell.

I've now requested all records of items matching that description to be sent to us, although whether such records exist is unclear so far.