There are some approaches to fixing the savegames.
First, make a backup copy of
Win Vista/7: %USERPROFILE%\Documents\Telltale Games\The Walking Dead
XP: %userprofile%\My Documents\Telltale Games\The Walking Dead\
(International users: Also exchange "My Documents" for the translation into your language)
before, just in case.
Mac: ~/Library/Application Support/Telltale Games/TheWalkingDead/
Restoring the savegame folder
It's easy if available on your system, but you will lose any progress since the last restore point.
PC: You can try the "restore previous version" feature on the savegame folder (right click, "properties", "restore previous version").
Mac: You might be able to restore the savegames using "time machine".
Manually fixing a savegame
This approach is a last resort and takes a bit of work, but can restore access to the latest savegame in one slot. It won't show the right data for the save slot in-game, so continue the game to see if it worked. Be sure to adapt the instructions for the Episode your savegame is from.
PC: The
Siezemore fix
Mac: The
Nonz fix