This bug has been mentioned in other threads on these forums but it does not seem to be present in this ('Bug Reports Centre') thread. I would consider this bug critical and therefore believe it should be posted here as well.
Steps to reproduce
i. Start a mulit-player game and password-protect your civ.
ii. Once in the game, change the name of you civ.
iii. Save the game and exit.
iv. Try to resume the multi-player game. After choosing your civ and typing in the password, you are told 'wrong password' even though it's correct.
The problem
The problem is that you cannot get back into the game with your civ.
Attempted work-arounds
Things that have been tried by other members of these forums:
i. Directly modifying save files via hex editors to change the hashed password string to what it was before. However, this results in the game crashing to desktop when attempting to load the modified save file. It seems that save files have a checksum string at their end which is compared against file's contents. To quote an extract from 1.52 README:
Fix for competitive games: Password-protected saves can no longer be easily stripped of their passwords, and the assets checksum in the save can no longer be modified by external means
ii. Entering the game as an AI civ (if there is one in the game), voting for continuing the game without waiting for the human players, and then saving it. This save can then be loaded as the passwords seem to be stripped. Problems with that work-around: one turn would have been made for the human civs by AI during that previous load and save. More importantly, subsequent saves and loads result in the exactly same problem as before, with the game refusing to accept your password (or lack of it if you didn't set one on the 2nd load).
Acknowledgements
Thanks to roadkill15, Stargrove and eelektrik for their contributions to the forums regarding this problem.